1.4.0: Fullscreen improvement, Borderless option, Bug fixes

For Firefox version 128

Features:
- Add `uc.tweak.borderless` and `uc.tweak.sidebery-top-navbar`
- `--uc-buton-radius` to make customizing easier
- Increase margin around floating sidebar

Fixes:
- Incorrect variable names in `misc.css`
- Bookmark bar background
- Floating urlbar not staying open when hamburger menu is open
- Weird resize behavior with sidebar

Docs:
- New images in readme
- Add cli install instructions
- Add Userchrome Toggle configuration guide

Chore:
- Remove unused `toolbar.css` file

artifacts