Function mkdir

test/Errors.test.js:117–122

(
			/** @type {string} */ dir,
			/** @type {(err?: Error | null) => void} */ callback
		)

	},
	outputFileSystem: /** @type {import("../").OutputFileSystem} */ ({
		mkdir(
			/** @type {string} */ dir,
			/** @type {(err?: Error | null) => void} */ callback
		) {
			callback();
		},
		writeFile(
			/** @type {string} */ file,
			/** @type {string | Buffer} */ content,