Scaffold out basic markdown language server (#154293)

* Scaffold out basic markdown lsp

This scaffolds out a new markdown language server and then uses it to implement document symbols. After the change, the markdown extension will have the following structure:

- languageService — Where all the LSP language stuff will eventually land
- server — The actual language server. Consumes ` languageService`
- src — The current extension that launches the server and implements VS Code specific functions

* Adding build scripts

* a

* Use language service from github

* Remove ls build scripts

* Bump versions

* Only build ext

* Enable for web

* Fixing for browser

extensions/markdown-language-features/src/languageFeatures/documentSymbols.ts

@@ -75,11 +75,3 @@ export class MdDocumentSymbolProvider implements vscode.DocumentSymbolProvider {
 		return '#'.repeat(entry.level) + ' ' + entry.text;
 	}
 }
-
-export function registerDocumentSymbolSupport(
-	selector: vscode.DocumentSelector,
-	tocProvider: MdTableOfContentsProvider,
-	logger: ILogger,
-): vscode.Disposable {
-	return vscode.languages.registerDocumentSymbolProvider(selector, new MdDocumentSymbolProvider(tocProvider, logger));
-}