Remove const enum from Level TypeScript definition (#295)

types/index.d.ts

@@ -1,7 +1,7 @@
 // Type definitions for Chalk
 // Definitions by: Thomas Sauer <https://github.com/t-sauer>
 
-export const enum Level {
+export enum Level {
 	None = 0,
 	Basic = 1,
 	Ansi256 = 2,

types/tsconfig.json

@@ -4,6 +4,7 @@
 		"target": "es6",
 		"noImplicitAny": true,
 		"noEmit": true,
-		"allowJs": true
+		"allowJs": true,
+		"isolatedModules": true
 	}
 }