Add Command Prefix

[BertilBraun]

Add an extra Options field where a "Command Prefix" can be entered.

I'm coming from VS Code where I use the command palette normaly to open files but with a prefix of ">" any command can be executed. Since you already have the Prefix logic implemented, a simple Prefix for Commands should be relativly easy to implement.

This would allow swapping the default behaviour of the command palette to be what ever a user wishes.

Let me know if you want help with this feature. I haven't yet taken a look at your project but that should be doable.