Add command to reopen the rebase editor after it was closed

[tudortimi]

Description

I closed the rebase editor, but I can't find a quick way to open it back. These are the only commands that exist related to "rebase":

I have "open on paused rebase" turned off, because it's too disruptive:

Normally I would only interact with the rebase editor to start the rebase, but every now and then I might want to open it again.

I'm using version 17.10.0.