src/vs/workbench/services/extensionManagement/browser/webExtensionsScannerService.ts/WebExtensionsScannerService/scanUserExtensions
class WebExtensionsScannerService:	async scanUserExtensions(profileLocation: URI, scanOptions?: ScanOptions): Promise<IScannedExtension[]> {
		const extensions = new Map<string, IScannedExtension>();

		// Custom builtin extensions defined through `additionalBuiltinExtensions` API
		const customBuiltinExtensions = await this.readCustomBuiltinExtensions(scanOptions);
		for (const extension of customBuiltinExtensions) {
			extensions.set(extension.identifier.id.toLowerCase(), extension);
		}

		// User Installed extensions
		const installedExtensions = await this.scanInstalledExtensions(profileLocation, scanOptions);
		for (const extension of installedExtensions) {
			extensions.set(extension.identifier.id.toLowerCase(), extension);
		}

		return [...extensions.values()];
	}