src/vs/platform/extensionManagement/node/extensionManagementUtil.ts/getManifest
export function getManifest(vsix: string): Promise<IExtensionManifest> {
	return buffer(vsix, 'extension/package.json')
		.then(buffer => {
			try {
				return JSON.parse(buffer.toString('utf8'));
			} catch (err) {
				throw new Error(localize('invalidManifest', "VSIX invalid: package.json is not a JSON file."));
			}
		});
}