Improve hot keys

[liyongsea]

Today the hot keys are not very intuitive

• ctrl + space triggers suggestion
• ctrl to accpte

We could do:

• ctrl + space triggers suggestion
• then enter to accept

And even let user configurate the hot key

[putskan]

Additionally, in Mac the ctrl+space shortcut is pre-occupied by the language-toggling shortcut.

[abidlabs]

I would do tab to accept the suggestion please as that is consistent with the VSCode Copilot extension