Add support for markdown notebook renderers (#115191)

* Use shared webpack version instead of installing locally for simple-browser

* Use npm for building markdown preview

* render markdown in webview.

* update markdown preview height and offset

* Add basic custom notebook renderer point

* update css

* style update.

* update markdown header padding left

* Add example of loading katex to extend the markdown-it renderer

* Rename global to make clear it only applies to markdown-in

* hide/remove markdown preview

* Add wait for initial markdown preview rendering before showing notebook

* Add double click to switch to editing mode

* Fix markdown cells not getting updated after editing

* style polish

* notebook.experimental.useMarkdownRenderer

* switch render strategy.

* Adding very intial drag drop support for notebook markdown cells

* Implement drag/drop stubs for test classes

* Revert unrelated file changes

* Move markdown notebook math to own extension

* Add missing imports

Co-authored-by: rebornix <penn.lv@gmail.com>

extensions/markdown-language-features/webpack.notebook.js

@@ -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.
+ *--------------------------------------------------------------------------------------------*/
+const path = require('path');
+
+module.exports = {
+	entry: {
+		index: './notebook/index.ts'
+	},
+	module: {
+		rules: [
+			{
+				test: /\.tsx?$/,
+				use: 'ts-loader',
+				exclude: /node_modules/
+			}
+		]
+	},
+	resolve: {
+		extensions: ['.tsx', '.ts', '.js']
+	},
+	output: {
+		filename: '[name].js',
+		path: path.resolve(__dirname, 'notebook-out')
+	}
+};