[#293] Add documentation comments and tests for TS Definitions

Notable changes:
- Move index.d.ts from types/ to project root (needed for
  tsd-check module).
- Rename test.ts to index.test-d.ts and place it under root
  (needed for tsd-check module).
- Add tsd-check module to test Typescript Definitions.

Future Work:
The properties inverse, hidden, strikethrough and visible
of Chalk interface in index.d.ts needs to be documented.

index.d.ts

@@ -0,0 +1,325 @@
+// Type definitions for Chalk
+// Project: Chalk
+// Definitions by: Thomas Sauer <https://github.com/t-sauer>
+// Updated definitions by: George Gkasdrogkas <https://github.com/georgegkas>
+
+export const enum Level {
+	/**
+	 * All colors disabled.
+	 */
+	None = 0,
+
+	/**
+	 * Basic 16 colors support.
+	 */
+	Basic = 1,
+
+	/**
+	 * ANSI 256 colors support.
+	 */
+	Ansi256 = 2,
+
+	/**
+	 * Truecolor 16 million colors support.
+	 */
+	TrueColor = 3
+}
+
+export interface Options {
+	/**
+	 * Enable or disable Chalk.
+	 *
+	 * @default true
+	 */
+	enabled?: boolean;
+
+	/**
+	 * Specify the color support for Chalk. By default,
+	 * color support is automatically detected based on
+	 * the environment.
+	 */
+	level?: Level;
+}
+
+export interface Constructor {
+	/**
+	 * Return a new Chalk instance.
+	 */
+	new (options?: Options): Chalk;
+
+	/**
+	 * Return a new Chalk instance.
+	 */
+	(options?: Options): Chalk;
+}
+
+/**
+ * Detect whether the terminal supports color.
+ */
+export interface ColorSupport {
+	/**
+	 * The color level used by Chalk.
+	 */
+	level: Level;
+
+	/**
+	 * Return whether Chalk supports basic 16 colors.
+	 */
+	hasBasic: boolean;
+
+	/**
+	 * Return whether Chalk supports ANSI 256 colors.
+	 */
+	has256: boolean;
+
+	/**
+	 * Return whether Chalk supports Truecolor 16 million colors.
+	 */
+	has16m: boolean;
+}
+
+export interface Chalk {
+	(...text: string[]): string;
+
+	(text: TemplateStringsArray, ...placeholders: string[]): string;
+
+	/**
+	 * Return a new Chalk instance.
+	 */
+	constructor: Constructor;
+
+	/**
+	 * Enable or disable Chalk.
+	 *
+	 * @default true
+	 */
+	enabled: boolean;
+
+	/**
+	 * The color support for Chalk. By default, color
+	 * support is automatically detected based on the
+	 * environment.
+	 */
+	level: Level;
+
+	/**
+	 * Use HEX value to set text color.
+	 *
+	 * @param color - Hexadecimal value representing the desired color.
+	 *
+	 * @example
+	 *
+	 * import chalk from 'chalk';
+	 *
+	 * chalk.hex('#DEADED');
+	 */
+	hex(color: string): this;
+
+	/**
+	 * Use keyword color value to set text color.
+	 *
+	 * @param color - Keyword value representing the desired color.
+	 *
+	 * @example
+	 *
+	 * import chalk from 'chalk';
+	 *
+	 * chalk.keyword('orange');
+	 */
+	keyword(color: string): this;
+
+	/**
+	 * Use RGB values to set text color.
+	 *
+	 * @param r - red
+	 * @param g - green
+	 * @param b - blue
+	 */
+	rgb(r: number, g: number, b: number): this;
+
+	/**
+	 * Use HSL values to set text color.
+	 *
+	 * @param h - hue
+	 * @param s - saturation
+	 * @param l - lightness
+	 */
+	hsl(h: number, s: number, l: number): this;
+
+	/**
+	 * Use HSV values to set text color.
+	 *
+	 * @param h - hue
+	 * @param s - saturation
+	 * @param v - value
+	 */
+	hsv(h: number, s: number, v: number): this;
+
+	/**
+	 * Use HWB values to set text color.
+	 *
+	 * @param h - hue
+	 * @param w - whiteness
+	 * @param b - blackness
+	 */
+	hwb(h: number, w: number, b: number): this;
+
+	/**
+	 * Use HEX value to set background color.
+	 *
+	 * @param color - Hexadecimal value representing the desired color.
+	 *
+	 * @example
+	 *
+	 * import chalk from 'chalk';
+	 *
+	 * chalk.bgHex('#DEADED');
+	 */
+	bgHex(color: string): this;
+
+	/**
+	 * Use keyword color value to set background color.
+	 *
+	 * @param color - Keyword value representing the desired color.
+	 *
+	 * @example
+	 *
+	 * import chalk from 'chalk';
+	 *
+	 * chalk.bgKeyword('orange');
+	 */
+	bgKeyword(color: string): this;
+
+	/**
+	 * Use RGB values to set background color.
+	 *
+	 * @param r - red
+	 * @param g - green
+	 * @param b - blue
+	 */
+	bgRgb(r: number, g: number, b: number): this;
+
+	/**
+	 * Use HSL values to set background color.
+	 *
+	 * @param h - hue
+	 * @param s - saturation
+	 * @param l - lightness
+	 */
+	bgHsl(h: number, s: number, l: number): this;
+
+	/**
+	 * Use HSV values to set background color.
+	 *
+	 * @param h - hue
+	 * @param s - saturation
+	 * @param v - value
+	 */
+	bgHsv(h: number, s: number, v: number): this;
+
+	/**
+	 * Use HWB values to set background color.
+	 *
+	 * @param h - hue
+	 * @param w - whiteness
+	 * @param b - blackness
+	 */
+	bgHwb(h: number, w: number, b: number): this;
+
+	/**
+	 * Modifier: Resets the current color chain.
+	 */
+	readonly reset: this;
+
+	/**
+	 * Modifier: Make text bold.
+	 */
+	readonly bold: this;
+
+	/**
+	 * Modifier: Emitting only a small amount of light.
+	 */
+	readonly dim: this;
+
+	/**
+	 * Modifier: Make text italic. (Not widely supported)
+	 */
+	readonly italic: this;
+
+	/**
+	 * Modifier: Make text underline. (Not widely supported)
+	 */
+	readonly underline: this;
+
+	/**
+	 * Modifier: Inverse background and foreground colors.
+	 */
+	readonly inverse: this;
+
+	/**
+	 * Modifier
+	 */
+	readonly hidden: this;
+
+	/**
+	 * Modifier
+	 */
+	readonly strikethrough: this;
+
+	/**
+	 * Modifier
+	 */
+	readonly visible: this;
+
+	readonly black: this;
+	readonly red: this;
+	readonly green: this;
+	readonly yellow: this;
+	readonly blue: this;
+	readonly magenta: this;
+	readonly cyan: this;
+	readonly white: this;
+	readonly gray: this;
+	readonly grey: this;
+	readonly blackBright: this;
+	readonly redBright: this;
+	readonly greenBright: this;
+	readonly yellowBright: this;
+	readonly blueBright: this;
+	readonly magentaBright: this;
+	readonly cyanBright: this;
+	readonly whiteBright: this;
+
+	readonly bgBlack: this;
+	readonly bgRed: this;
+	readonly bgGreen: this;
+	readonly bgYellow: this;
+	readonly bgBlue: this;
+	readonly bgMagenta: this;
+	readonly bgCyan: this;
+	readonly bgWhite: this;
+	readonly bgBlackBright: this;
+	readonly bgRedBright: this;
+	readonly bgGreenBright: this;
+	readonly bgYellowBright: this;
+	readonly bgBlueBright: this;
+	readonly bgMagentaBright: this;
+	readonly bgCyanBright: this;
+	readonly bgWhiteBright: this;
+}
+
+/**
+ * Main Chalk object that allows to chain styles together.
+ * Call the last one as a method with a string argument.
+ * Order doesn't matter, and later styles take precedent in case of a conflict.
+ * This simply means that `chalk.red.yellow.green` is equivalent to `chalk.green`.
+ */
+declare const chalk: Chalk & { supportsColor: ColorSupport };
+
+/**
+ * Alias Options and Constructor to preserve backwards compatibility.
+ */
+export type ChalkOptions = Options;
+export type ChalkConstructor = Constructor;
+
+export default chalk