Feature Request

• This is a feature request and I have read the contribution guidelines.

Description

Streamlink should provide shell completions for all of its parameters. This could either be static and simple, or a bit more sophisticated and dynamic, depending on the allowed parameter values. Completion data for multiple shells, like fish for example, would also be nice.

I've checked a couple of solutions that work in conjunction with argparse, so that shell scripts don't have to be written manually and maintained next to the regular parameter definitions. This can be done with argcomplete for example, but it needs to run before streamlink-cli's own code gets executed and also needs to be added as a dependency (obviously), and I'm not sure if that's desired.

If there's a way to generate shell completion scripts from argparse, then this would be the best solution.