Enable Pipewire by default in Firefox

Enabling the experimental setting media.webrtc.camera.allow-pipewire in about:config allows devices to use Pipewire and therefore libcamera. It's already set in the mobile-config but on laptops like the Thinkpad X13s that is not installed.

Let's enable it somehow.

Note:

1. Fedora 41 will do it as well, which means it got a lot of QA from RH folks lately, fixing a bunch of remaining issues.
2. The main caveat for pmOS is likely that it requires the xdg-destop-portal to work, see e.g. !5643

---

cc @craftyguy @pabloyoyoista - opening this issue as a reminder as it came up during the hackfest

I wonder in which package this should be, a seperate postmarketos-firefox package, upstream at Alpine's firefox?

Alpine's firefox simply installs a vendor.js file to /usr/lib/firefox{,-esr,-developer-edition}, so that should be easy enough:

	# install our vendor prefs
	install -Dm644 "$srcdir"/vendor-prefs.js \
		"$pkgdir"/$_mozappdir/browser/defaults/preferences/vendor.js

pref("media.webrtc.camera.allow-pipewire", true);

I guess the problem there is the portal, but having a subpackage upstream with install_if=firefox portal might make sense. @fossdd do you want to take that conversation upstream?

Yeah, sure

added camera typefeature labels