Add own apparmor profile to deb package

per @boklm's comment in mullvad-browser#348 (closed)

It looks like they don't need to do anything because the apparmor package in Ubuntu 24.04 provides a default apparmor policy for firefox in /etc/apparmor.d/firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1884347#c17

But this policy didn't work for Beta/DevEdition/Nightly, so they started working on a patch adding an apparmor policy file, but in the end it has not been needed since upstream fixed their default policy: https://bugzilla.mozilla.org/show_bug.cgi?id=1884980

In our case it looks like we'll need to ship some policy file in the deb package.