exists(url) {
		return new Promise((resolve, reject) => {
			reject = setMessage(reject);
			window.resolveLocalFileSystemURL(
				url,
				(entry) => {
					resolve(true);
				},
				(err) => {
					if (err.code === 1) resolve(false);
					reject(err);
				},
			);
		});
	}
Check if a file or directory exists
@param {Promise<Boolean>} url