Fixes #42955

Fixes #43869

Fixes #43619

* Webview api

* Cleaning up markdown webview

* Hooking up dispose

* Fix some merge errors

* Use custom context key to show markdown title bar contributions

* Add basic on focus and on blur events

* Fixing find widget in webview

* Hookup _isDisposed

* Use new extension resource scheme to load markdown extension resources

* Documenting keep alive

* Fixing trailing spaces in expansion

* Emmet - Fixing extra spaces when wrapping with abbreviation

* Avoid fetching tag if there's no need to ezpand again

* Replacing several 'indexof's with regexp

* Making regexp for tagname stricter. Removing unnecessary check.

* Removing extra call to expand.

* tiny changes

* tinitiny changes

* Get emmet completions from html,css extensions

* Resolve extensionsPath, use emmet results even if empty

* Support css abbr with :

* Refactoring

* Add some basic emmet tests

* Refactoring

* More tests

* Updated monokai dropdown configuration to use new dropdown.listBackground property

Fixes #42583