Allow command submission in a little editor

[jisantuc]

brick has an example of a simple editor: https://github.com/jtdaugherty/brick/blob/master/programs/EditDemo.hs

When users press Enter with a script selected, we should pop open an editor that's prefilled with ./scripts/<selected name>, that shows the --help output, and that allows submitting the command on ctrl+Enter or something similar.

stdout can be thrown away for now until I verify that this whole plan even works.