feat: add qrca as system flatpak (#229)

I reinstalled Aurora on my laptop and afterwards I wanted to connect to
another WiFi Network other than the one I specified in Plasma Setup and
in the network applet you have the option to scan a QR-Code with the
camera and connect to the wifi that way, if we preinstall qrca[1] then
this is just gonna work out of the box.

For desktops it wouldn't be useful for this purpose, but at least you
could still scan QR-Codes from images.

It's a small KDE app so I think it's fine to include by default.

[1]: https://github.com/flathub/org.kde.qrca

Author: renner0e

system_files/shared/usr/share/ublue-os/homebrew/system-flatpaks.Brewfile

@@ -17,6 +17,7 @@ flatpak "org.kde.kclock"
 flatpak "org.kde.kontact"
 flatpak "org.kde.kweather"
 flatpak "org.kde.okular"
+flatpak "org.kde.qrca"
 flatpak "org.kde.skanpage"
 flatpak "org.mozilla.thunderbird"
 flatpak "org.mozilla.firefox"