extensions/html-language-features/client/src/customData.ts/getCustomDataPathsFromAllExtensions
function getCustomDataPathsFromAllExtensions(): string[] {
	const dataPaths: string[] = [];
	for (const extension of extensions.all) {
		const customData = extension.packageJSON?.contributes?.html?.customData;
		if (Array.isArray(customData)) {
			for (const rp of customData) {
				dataPaths.push(joinPath(extension.extensionUri, rp).toString());
			}
		}
	}
	return dataPaths;
}