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/server/.vscode/tasks.json

@@ -0,0 +1,9 @@
+{
+	"version": "0.1.0",
+	"command": "npm",
+	"isShellCommand": true,
+	"showOutput": "silent",
+	"args": ["run", "watch"],
+	"isWatching": true,
+	"problemMatcher": "$tsc-watch"
+}