Provide keyboard shortcut to open textual editor in another editor group when Kaoto editor is opened

[apupier]

requires #492

Maybe use Ctrl+K V, which is already used by default to Open preview to the Side for Markdown. I remembered that some other "preview" are reusing this one or Ctrl+Shift+V

https://code.visualstudio.com/docs/getstarted/keybindings#_display

This can be defined in packge;json: https://code.visualstudio.com/api/references/contribution-points#contributes.keybindings