Fix for KeePassXC browser integration

Out of the box a browser installed via Flatpak can't communicate with KeePassXC using the browser extension because of Flatpaks encapsulation.

This can be fixed by adjusting the browsers Flatpak permissions, adding a wrapper for keepassxc-proxy to the browsers container and spawning keepassxc-proxy from within the container.

I built a script that does this for you. Currently supports Firefox, Librewolf and Ungoogled Chromium.

Have fun!