chore: add JSDoc returns information (#33)

Author: Trott

Diff for: index.js

@@ -14,6 +14,7 @@ var escaped = /\\([\!\*\?\|\[\]\(\)\{\}])/g;
  * @param {string} str
  * @param {Object} opts
  * @param {boolean} [opts.flipBackslashes=true]
+ * @returns {string}
  */
 module.exports = function globParent(str, opts) {
   var options = Object.assign({ flipBackslashes: true }, opts);