PopOS! Changed to Flatpak by default

[SteveClement]

Checking for deb-src on the latest PopOS! install fails.

After uprgrading i3-gaps-deb fails with:

➜ ./i3-gaps-deb
[igd] This tool creates (and optionally installs) Debian packages of i3-gaps... [RETURN]
[igd] This tool comes without any warranty and in the hope to be useful... [RETURN]
[igd] Checking i3 installation...
[igd] Checking sources.list(s) to contain sources ("weak")...
[igd] Please add necessary "deb-src" line(s) to your apt sources (and run an 'apt update'). [RETURN]

The fix would be to change Line 95:

if ! grep --quiet -r "^ *deb-src.*\(\(debian\)\|\(ubuntu\)\|\(kali\)\|\(ascii\)\|\(beowulf\)\)[/ ].*main" /etc/apt/sources.list*; then

To something flatpak compatible.

I can send a PR if it is not already in the works.