Add support for daemonization

[skrashevich]

This pull request introduces several enhancements and updates to the project. The major additions are as follows:

• Daemonization Support: Added functionality to run the program as a daemon with the -d flag. This allows the program to run as a background process.
• Dropping privileges: Introduced a flag to specify the user that the program should run as. For example, go2rtc might need root permissions in order to bind to a network port number lower than 1024 (as is the case in many Unix-like systems), but it does not need those permissions to handle incoming network connections once the port is open.
• Signal Handling: Added signal handlers for SIGQUIT, SIGTERM, SIGSEGV, and SIGHUP. This improves the program's ability to handle different types of system signals and makes the program more robust. Additionally, the signal notifications in the shell package have been updated to include SIGQUIT and SIGSEGV.

All these changes apply only to unix-like systems. for windows stubs are implemented

[AlexxIT]

Lots of code. It needs to be carefully analyzed all of it.

[skrashevich]

Lots of code. It needs to be carefully analyzed all of it.

The Way of the Maintainer :)

[skrashevich]

Up 🙄