Update the flatpak on flathub to newest version

[T3sT3ro]

Hello, flatpak version of shadered on flathub is still on 1.5.4. Please, if you have time, publish the newest version

[reaply]

I do understand that Cali is an extremely busy person with Godot and other projects, but an updated Flatpak would be appreciated. It's been quite difficult to get it to run on Popos due to it requiring LibGlew 2.1 and Popos uses 2.2.

I'm still attempting to get 2.2 to work but I'm not that great at getting software to compile.