fixes #64377

Fixes #63741

Fixes #64387

ES6 promises like using undefined as their first argument instead of null. Both should behave the same behavior

Fixes #62892

`guessMimeTypes` can be changed by extensions. This is not desirable for webviews. Just hardcode a list of common mimes to use for webview content

Part of #60565

fixes #63145

These methods return an IEditor as a result but even if the opening fails or the editor was not opened as active.

The fix is to check for the result of the open call and only return the editor if the editor was opened actually.

This restores the behaviour we had before GRID.

fixes #64767

fixes #64233

* Completely hide tab close button when dirty state is highlighted in top border

* Use :not selector to avoid code duplication

Try to better support handle of unicode in markdown by using a word definition that use unicode character class

Fixes #15177