Use AUR packages instead of installing extensions manually

[aartoni]

This update streamlines larbs.sh by installing Librewolf extensions via their respective AUR packages.

The AUR build process is somewhat similar to manual installation in that it still downloads the .xpi files. However, the difference is that makepkg performs integrity checks and installs the package globally (for all users). This global installation should not be an issue, as we are already installing arkenfox-user.js globally.

This PR also includes two additional changes:

• Decentraleyes has been replaced with LocalCDN, as Decentraleyes is no longer maintained.
• Vim Vixen has been replaced with Tridactyl, the OG Vim extension, which is actively maintained.

As a sidenote: once this is merged, expect another PR to add Tridactyl Native, enabling configuration of Tridactyl from a file. This will help achieve feature parity with Vim Vixen, as Tridactyl has a few inconvenient defaults (notably the scroll height and the "next" binding for searches).