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/notebook/index.ts

@@ -0,0 +1,29 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as MarkdownIt from 'markdown-it';
+
+declare const acquireNotebookRendererApi: any;
+type extendMarkdownItFnType = (
+	(f: (md: MarkdownIt.MarkdownIt) => void) => void
+);
+
+(function () {
+	const markdownIt = new MarkdownIt();
+
+	(globalThis as any).extendMarkdownIt = ((f: (md: MarkdownIt.MarkdownIt) => void) => {
+		f(markdownIt);
+	}) as extendMarkdownItFnType;
+
+	const notebook = acquireNotebookRendererApi('notebookCoreTestRenderer');
+
+	notebook.onDidCreateMarkdown(({ element, content }: any) => {
+		console.log('did create markdown cell');
+		const rendered = markdownIt.render(content);
+		element.innerHTML = rendered;
+	});
+
+	console.log('markdown-it');
+}());