When backspacing at the beginning of the line (except for whitespace), move content to the previous line

[5GameMaker]

Right now you need to remove all backspace to move content to the previous line, and if it was empty you'll need to manually indent it (or run the formatter).

Instead, just move content to the previous line removing all leading whitespace.

Current behavior:
https://github.com/user-attachments/assets/316fe146-25cc-480b-a78a-2544db23766b (github doesn't like videos :<)