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-notebook-math/notebook/extension.ts

@@ -0,0 +1,22 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import type * as markdownIt from 'markdown-it';
+
+import 'katex/dist/katex.min.css';
+
+declare const extendMarkdownIt: undefined | (
+	(f: (md: markdownIt.MarkdownIt) => void) => void
+);
+
+(function () {
+	const katex = require('@iktakahiro/markdown-it-katex');
+
+	if (typeof extendMarkdownIt !== 'undefined') {
+		extendMarkdownIt((md: markdownIt.MarkdownIt) => {
+			md.use(katex);
+		});
+	}
+}());
+

extensions/markdown-notebook-math/notebook/tsconfig.json

@@ -0,0 +1,12 @@
+{
+	"extends": "../../shared.tsconfig.json",
+	"compilerOptions": {
+		"outDir": "./dist/",
+		"jsx": "react",
+		"lib": [
+			"es2018",
+			"DOM",
+			"DOM.Iterable"
+		]
+	}
+}