Provide TypeScript declaration

[til-schneider]

You should provide a TypeScript declaration, so copy-text-to-clipboard can seamlessly be used in TypeScript. This would also provide auto-completion for JavaScript users in some editors.

Just add a file called index.d.ts with the following content:

/**
 * Copy `text` to the clipboard.
 * Must be called in response to a user gesture event, like `click` or `keyup`.
 *
 * @return whether copying succeeded
 */
export default function copy(text: string): boolean

[sindresorhus]

Fixed by #24