provide editdor as a VS Code extension

[fennibay]

Using editdor via browser is fine and easy. However some aspects could be improved if it would also be available as a VS Code extension:

1. Working easier with local files
2. Working with other TDs and other files inside a bigger project
3. Source control (git) integration

For example, draw.io offers a web editor as well as a VS Code extension and also a desktop editor.

cc: @rhofer @fexpal