[feature request] flatpak walker builds

[gmankab]

• with flaptaks there are no dependencies problems
• flatpaks works same in all distros
• if you providing flatpak builds, there are no need to build binaries for every single distro
• flatpaks are main way to install apps on atomic distros, like fedora atomic, vanilla os, and steam os

[gmankab]

also it would be nice to have binary builds on aur and on fedora copr

[abenz1267]

I see the appeal.

Feel free to open a PR.