Expose pyav keyword arguments

[nitanmarcel]

The following pyav keyword arguments needs to be exposed to the user when passing a source to tgcalls:

format

• Specific format to use. While ffmpeg does a great job in detecting a source format sometimes might fail or give false results. This argument allows the user to specify what format the given source uses.

options 

• Any option you'll pass to the ffmpeg client you'll pass here. Including custom user agents, headers, framerate options, size option (useful for resizing videos)

timeout 

• Exactly as in the [documentation](https://pyav.org/docs/develop/api/_globals.html?highlight=open#av.open) How many seconds to wait for data before giving up, as a float, or a (open timeout, read timeout) tuple.