build/lib/extensions.ts/updateExtensionPackageJSON
function updateExtensionPackageJSON(input: Stream, update: (data: any) => any): Stream {
	const packageJsonFilter = filter('extensions/*/package.json', { restore: true });
	return input
		.pipe(packageJsonFilter)
		.pipe(buffer())
		.pipe(es.mapSync((f: File) => {
			const data = JSON.parse(f.contents.toString('utf8'));
			f.contents = Buffer.from(JSON.stringify(update(data)));
			return f;
		}))
		.pipe(packageJsonFilter.restore);
}