src/vs/platform/files/common/inMemoryFilesystemProvider.ts/InMemoryFileSystemProvider/mkdir
class InMemoryFileSystemProvider:	async mkdir(resource: URI): Promise<void> {
		let basename = resources.basename(resource);
		let dirname = resources.dirname(resource);
		let parent = this._lookupAsDirectory(dirname, false);

		let entry = new Directory(basename);
		parent.entries.set(entry.name, entry);
		parent.mtime = Date.now();
		parent.size += 1;
		this._fireSoon({ type: FileChangeType.UPDATED, resource: dirname }, { type: FileChangeType.ADDED, resource });
	}