Suggest adding gcc, ffmpeg, and portaudio19-dev to requirements.txt

[nixkuroi]

After trying to install with pip install -r requirements, it errored out saying that gcc wasn't installed. Following that, it failed to build the wheel for pyaudio until I installed portaudio19-dev.

I suggest adding those two dependencies to requirements.txt file.

[mallorbc]

A PR that does this correctly with the toml would be accepted.