Independent signal handler for Unix signals

[pmk21]

Requested Feature
Add a separate signal handler, for better handling of Unix signals.

Suggested Solution
The signal-hook crate could be used to create signal handlers.

Additional context

rshark/src/display/ui.rs

Line 150 in 7158a19

Key::Char('q') | Key::Ctrl('c') => {

For example here Ctrl + C is a SIGINT signal which could be handled by a signal handler instead of handling it as a keyboard event.

This probably needs further discussion before any action is taken. Feel free to comment below

[AkshathaLaxmi]

Hi! A problem I see with the solution that is suggested is that rshark might not work in a Windows environment due to signal-hook not having support for signals in Windows. Maybe an alternative would be to use the crate ctrlc?

[pmk21]

Right now I don't think even rshark works for Windows. But ctrlc seems a better choice if we later decide to support Windows.