Try to revoke tokens that are getting deleted

Best effort.

Fixes https://github.com/microsoft/vscode/issues/152055

extensions/github-authentication/src/node/buffer.ts

@@ -0,0 +1,8 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export function base64Encode(text: string): string {
+	return Buffer.from(text, 'binary').toString('base64');
+}