Introduce unit tests for monaco-editor-react

[kaisalmen]

We already introduced multiple unit tests for monaco-editor-wrapper, but don't have any for monaco-editor-react.
This is not as straightforward as initially thought. It is likely the combination of vitest with browser mode and react. I already started some prototyping on https://github.com/TypeFox/monaco-components/tree/vitest-react