Migrate github extension to ESM (2nd attempt) (#248312)

* Revert "GitHub - revert ESM migration (#247322)"

This reverts commit 2047ab0fff.

* use `"@vscode/extension-telemetry": "^1.0.0"` which doesn't use default export anymore

extensions/github/extension.webpack.config.cjs

@@ -0,0 +1,27 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+//@ts-check
+
+'use strict';
+
+const withDefaults = require('../shared.webpack.config');
+
+module.exports = withDefaults({
+	context: __dirname,
+	entry: {
+		extension: './src/extension.ts'
+	},
+	output: {
+		libraryTarget: 'module',
+		chunkFormat: 'module',
+	},
+	externals: {
+		'vscode': 'module vscode',
+	},
+	experiments: {
+		outputModule: true
+	}
+});