Save last-entered branch in create workflow dialogue

Description of the feature request

Retain the last-used branch in create workflow dialogue

Use case / for what or how I would use it

This would save a bit of frustration. At the moment, I’m testing a workflow, so not using a git event to trigger it. I’m using a different branch to test again, and every time I go to create a new workflow, I have to re-enter the branch name. An example branch name is “49-get-ios-build-working” - that’s easier to copy/paste from my git client than try to remember manually, but I because we all copy/paste all the time, I have to keep switching to the git client, re-copying it, re-pasting it into Bitrise etc.