Upgrade typescript- and linting-dependencies

Attempts to fix linter parsing issues stemming from changes in typescript v3.7.

- Upgrade `eslint`-related packages.
- Upgrade `typescript` and related `@sindresorhus/tsconfig`.
- Fixes linting errors due to upgraded rules.
- Note that you might need to remove `node_modules` and run `npm install` again to properly clear linting caches.
- Include the `test` directory in a separate `tsconfig.xo.json` to fix the below parsing error.

> Parsing error: `"parserOptions.project"` has been set for `@typescript-eslint/parser`.
> The file does not match your project config: `test/test.ts`.
> The file must be included in at least one of the projects provided.

See

- https://github.com/typescript-eslint/typescript-eslint/pull/1045
- https://github.com/microsoft/TypeScript/commits/v3.7.5
- https://github.com/sindresorhus/tsconfig/issues/7
- https://github.com/xojs/eslint-config-xo-typescript/issues/20
- https://github.com/xojs/eslint-config-xo-typescript/issues/15

package.json

@@ -46,20 +46,20 @@
 		"types"
 	],
 	"devDependencies": {
-		"@sindresorhus/tsconfig": "^0.6.0",
+		"@sindresorhus/tsconfig": "^0.7.0",
 		"@types/jsdom": "^12.2.4",
 		"@types/node": "^12.12.6",
 		"@types/zen-observable": "^0.8.0",
-		"@typescript-eslint/eslint-plugin": "^1.11.0",
-		"@typescript-eslint/parser": "^1.11.0",
+		"@typescript-eslint/eslint-plugin": "^2.17.0",
+		"@typescript-eslint/parser": "^2.17.0",
 		"ava": "^2.1.0",
 		"del-cli": "^2.0.0",
-		"eslint-config-xo-typescript": "^0.15.0",
+		"eslint-config-xo-typescript": "^0.24.1",
 		"jsdom": "^15.0.0",
 		"rxjs": "^6.4.0",
 		"tempy": "^0.3.0",
 		"ts-node": "^8.3.0",
-		"typescript": "^3.7.2",
+		"typescript": "^3.7.5",
 		"xo": "^0.25.3",
 		"zen-observable": "^0.8.8"
 	},
@@ -80,6 +80,9 @@
 		"extensions": [
 			"ts"
 		],
+		"parserOptions": {
+			"project": "./tsconfig.xo.json"
+		},
 		"globals": [
 			"BigInt",
 			"BigInt64Array",