build: add debian packaging files

[drlkf]

This pull request introduces debian packaging files. There are 2 most important items:

1. Icons and server download are added to the cmake build
2. An edge-case is introduced in the server load path to avoid putting a server.js in /usr/bin on debian package installs

I've added the instructions to build the package in the DEBIAN.md file, let me know if something is missing or unclear.

cheers

[drlkf]

Any chance we could get some attention to this?

[kzdnk]

I know very little of debian packaging, so I can't talk about correctness, but I tested this on bookworm and it seems to be working fine.

One thing I had to do, that is not mentioned, is to enable the non-free archive for libfdk-aac2.

[kzdnk]

Also, desktop entry is displayed with the default icon.

[drlkf]

Both should be fixed now