allow PPA in apt-packages to permit various repositories

[danhs]

I wanted to install lazygit.
I wanted to add its PPA so that I could install lazygit via apt-packages.

This would be a very great logical extension of this feature.

Thanks very much for all of your work maintaining this feature. I appreciate it

[eitsupi]

Thanks.

As I understand it, add-apt-repository command has been deprecated, so I'm not sure what the proper way is (which is why I didn't implement it in this Feature).

I'm not familiar enough with apt, so if there is a proper and up-to-date method, I'd welcome contributions.