src/vs/platform/files/browser/htmlFileSystemProvider.ts/HTMLFileSystemProvider/writeFile
class HTMLFileSystemProvider:	async writeFile(resource: URI, content: Uint8Array, opts: FileWriteOptions): Promise<void> {
		const handle = await this.getFileHandle(resource);

		if (!handle) {
			throw new Error('File not found.');
		}

		const writable = await handle.createWritable();
		await writable.write(content);
		await writable.close();
	}