* Improve codeblock formatting in documentation
Improves codeblock highlighting by:
- Adding context to the codeblock detailing which language the
following code is.
- Setting the `pre` block's background to match the default
background for `code` blocks to give a consistent experience.
- Setting a border radius for the `pre` block double that of the
`code` block's default (4px, which is hard-coded).
* Updated Godot icons (and removed old ones)
* Improve "Debug Pinned Scene" command by making the pinned scene persist between VSCode sessions
* Fix scene file highlighting not working
* Fix ScenePreview not working in Godot 3
* Add buttons for relevant actions to ScenePreview items
* Add internal document links for SubResource() and ExtResource() statements in scene files
* Add hover for SubResource() and ExtResource() statements in scene files
* Improve ability to right click -> open docs for methods of builtin types (doesn't always work)
* Add a file decorator to show the pinned debug file in the filesystem view/editor tabs
* Add item decorators to the Scene Preview to show Node attributes more clearly
* Updated readme
* Overhauled documentation viewer
* Added GDScript formatter
* Add (disabled) experimental providers for custom completions, semantic tokens, and tasks
* Lots of internal refactoring
