Added proper themes for GTK apps

[SakibShahariar]

Description

This makes the gtk apps more vibrant with proper css for both gtk3 and gtk4 and probably flatpak too.

Changes

• Improved
• Bug Fixes
• Feature
• Documentation
• Other

Context

Regular theme doesn't look that good, that's why I want to add this.

How Has This Been Tested?

• Tested on Arch Linux/Based Distro.
• Tested on Fedora Linux/Based Distro.
• Tested on openSuse.

Checklist

Please ensure your pull request meets the following requirements:

• My code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• My changes do not introduce new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes.

Screenshots

Additional Notes

Check if gtk4 apps are looking right. Also check gtk3 apps, and flatpak apps. If doesn't work, we need to set theme using gsettings and for flatpak need to set up it's theme.

[mylinuxforwork]

Thank you vety much. I like what I see in your screenshot. But, Does This require so many files? Is there a way to only change the colors without adding all the icons?

[SakibShahariar]

Yeah, there are many svg icons. Basically, I downloaded gruvbox gtk theme and edited the css files to match matugen. So, I didn't pay that much attention to the assets folder. I guess it should work without those but you should check yourself or I can check tomorrow and confirm if they needed or not.

[SakibShahariar]

I checked and they can be removed by editing the css files. But svg icons are really small and don't take much space(less than 1 mb total) . But if you want I can edit them.

[mylinuxforwork]

I checked and they can be removed by editing the css files. But svg icons are really small and don't take much space(less than 1 mb total) . But if you want I can edit them.

If you have time, it would be great.

[SakibShahariar]

ok I will edit them. Btw, check if they work for different apps like normal gtk3 and gtk4, flatpak apps and root accessed apps like gparted

[mylinuxforwork]

ok I will edit them. Btw, check if they work for different apps like normal gtk3 and gtk4, flatpak apps and root accessed apps like gparted

Great.