createDir(path, dirname) {
		return new Promise((resolve, reject) => {
			reject = setMessage(reject);
			window.resolveLocalFileSystemURL(
				path,
				(fs) => {
					fs.getDirectory(
						dirname,
						{ create: true },
						async () => {
							const stats = await this.stats(Url.join(path, dirname));
							resolve(stats.url);
						},
						reject,
					);
				},
				reject,
			);
		});
	}
Create a directory
@param {string} path
@param {string} dirname
@returns {Promise}