[FEATURE REQUEST] Add Github as a "package manager"

### Please confirm these before moving forward.

- [x] I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue.
- [x] This proposal is a completely new feature. If you want to suggest an improvement or an enhancement, please use [this template](https://github.com/Devolutions/UniGetUI/issues/new?labels=enhancement&projects=&template=enhancement-improvement.yml&title=%5BENHANCEMENT%5D+%28Enter+your+description+here%29).

### Describe the new feature

It would be life-changing to have such functionality. There is an app, [Obtainium](https://github.com/ImranR98/Obtainium), that does this on Android, and it would be great to have something like this on Windows.

### Describe how this new feature could help users

I know it’s not exactly like a package manager, but the idea is:

To have organized programs from GitHub
To keep track of updates

Obtainium does this well, and since it's open source, I guess some of its code or ideas could be used.

Obviously, there is a lot of stuff on GitHub, but I would suggest adding functionality to track new releases for any repository, along with installation options for Windows executables.

For portable .exe files, "installing" could simply mean downloading the file and creating shortcuts on the desktop and Start menu.
For installers, it would just launch them.