user.js path for Flatpak Firefox

[jroddev]

For the Flatpak version of Firefox the Profile Directory shown on about:support doesn't exist.
The correct place to put user.js is
$HOME/.var/app/org.mozilla.firefox/.mozilla/firefox/<profile name>/

Tested on AuroraOS (uBlue)

I couldn't see this mentioned anywhere. If it is then feel free to close issue.
Otherwise it might be helpful to add it here https://github.com/yokoffing/Betterfox/wiki/Backup