Add TypeScript types

index.d.ts

@@ -0,0 +1,31 @@
+export type Format = (string: string) => string;
+
+export const reset: Format;
+export const bold: Format;
+export const dim: Format;
+export const italic: Format;
+export const underline: Format;
+export const overline: Format;
+export const inverse: Format;
+export const hidden: Format;
+export const strikethrough: Format;
+
+export const black: Format;
+export const red: Format;
+export const green: Format;
+export const yellow: Format;
+export const blue: Format;
+export const magenta: Format;
+export const cyan: Format;
+export const white: Format;
+export const gray: Format;
+
+export const bgBlack: Format;
+export const bgRed: Format;
+export const bgGreen: Format;
+export const bgYellow: Format;
+export const bgBlue: Format;
+export const bgMagenta: Format;
+export const bgCyan: Format;
+export const bgWhite: Format;
+export const bgGray: Format;

index.test-d.ts

@@ -0,0 +1,4 @@
+import {expectType} from 'tsd';
+import * as colors from './index.js';
+
+expectType<string>(colors.red('x'));

package.json

@@ -16,7 +16,7 @@
 		"node": "^12.20.0 || ^14.13.1 || >=16.0.0"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
 		"index.js",
@@ -44,6 +44,7 @@
 	],
 	"devDependencies": {
 		"ava": "^3.15.0",
+		"tsd": "^0.17.0",
 		"xo": "^0.44.0"
 	}
 }