add DEB package for Electrum Wallet

[dav1app]

I'm drafting a PR to build the DEB package for the Electrum wallet.

⚠️ INB4: For some reason, it builds without the libsecp256k1-1, but the package fails to execute. I had to manually add the dependency (It is from the official deb repo)

stdeb is the only python3 dependency that it is required since we already have the setup.py structured.

The current command line to build it is:

setup.py --command-packages=stdeb.command bdist_deb

I'm not the most prominent Linux developer, so feel free to speak up.

[SomberNight]

Could you give some context? What is the goal of this PR? Also, isn't electrum already packaged by debian? Is that not enough? Also, there is a related PR: https://github.com/spesmilo/electrum/pull/5336

[dav1app]

Sorry Somber,

This main aims to add the .deb package build over the releases. It is fine to have it distributed over the official repositories, but distributing with the other packages allow one to download it as a standalone application.