Trim whitespace on save

[andyholmes]

Thanks for the great editor!

If possible, could you offer an option to trim whitespace on save? As a super bonus ensuring there's a single newline at the end of the file would be great, too.

[fabiocolacio]

I like this idea too. I know that plugins like this exist for other gtksourceview-based editors (Gedit, Pluma, elementary Code), so I might be able to add compatibility for existing plugins.