Vscode CI warning: Bundle extension

[mre]

We get the following warning when packaging the plugin:

This extension consists of 3177 files, out of which 2320 are JavaScript files. For performance reasons, you should bundle your extension: https://aka.ms/vscode-bundle-extension . You should also exclude unnecessary files by adding them to your .vscodeignore: https://aka.ms/vscode-vscodeignore

We should probably investigate on how to shrink bundle size. Pull requests welcome.