fix: add script to remove Plasma keyboard shortcuts

[nivaca]

Summary

Added script to remove Bismuth's keyboard shortcuts in ~/.config/kglobalshortcutsrc.

Breaking Changes

Do your changes intentionally break something on the user side or configuration?
No.

UI Changes

None.

Test Plan

1. Run sh remove_keyboard_shortcuts.sh
2. Answer y to confirm.
3. The keyboard shortcuts in ~/.config/kglobalshortcutsrc should be gone.

Related Issues

Closes #137

[gikari]

You need to rename your commit according to CC and add License headers.
Also, your script does not reload a shortcuts' daemon vial systemctl restart ..., so the change wouldn't work unless your login-logout to the session.