Add option to open DevTools

The more I use electron-debug, the more I'm annoyed by this use case. I open DevTools with toggle shortcut, then often it got covered by other windows, but still open. After a while, I often forgot it is open and I press toggle key to show DevTools, but since it's already opened, it close.

I think it should be useful to add an option to just open it if closed, or otherwise focus it. I don't think there is a specific method in electron to focus, we could ask for it (or maybe it could suffice to re-open it, I have to try).