Trim whitespace at the end of lines on save

[kyldvs]

I constantly find myself with extra white-space all throughout my sketches. I'm pretty sure this is a very common editor feature so would be desirable to add here too. Maybe prevent trimming currently focused line though.

[thangngoc89]

I'm not sure if this is a common editor behavior. VS Code doesn't behave like that :) . But refmt will definitely help here.

[kyldvs]

It's common enough that it has an option built into VSCode, perhaps this could be a configurable option for logged in users?

https://stackoverflow.com/questions/30884131/remove-trailing-spaces-automatically-or-with-a-shortcut