External maintainer proposal on Ubuntu systems (launchpad)

Hello @hluk,

I created an issue some time ago linked to this PR https://github.com/hluk/CopyQ/pull/3385. We discussed about the maintenance and other Qt issues regarding Ubuntu and other build systems.

I know you stated that you won't publish newer versions of this packages with these distro but here is my take https://github.com/Quentium-Forks/CopyQ

This is my own build chain for Debian, Rpm and AppImage. I have the similar tools setup for my project [Stacer](https://github.com/QuentiumYT/Stacer) and the one I maintain [nvtop](https://github.com/Quentium-Forks/nvtop).

If you're interested about some external maintenance for Ubuntu systems (like [nvtop on launchpad](https://launchpad.net/~quentiumyt/+archive/ubuntu/nvtop) with a stable and nightly release, I can do that :))
If you prefer merging this proposal, it's 100% automated, you just have to generate a base64 key for launchpad (but doesn't align entirely with your code structure I know). I can keep a separate fork like I'm doing with nvtop.

Let me know your thoughts :)
Have a nice day