[FR]: Add audio mixer feature

[Fyphen1223]

Description

Add the audio mixer feature to NodeLink. Enables NodeLink to take multiple audio stream into one single stream and play it.

Reason

This can be useful in some bots, such as TTS bots.

Example code

No response

Confirmations

• [X] This feature is not already implemented.
• [X] I have verified that this is not a duplicate feature request.

Code of Conduct

• [X] I agree to follow this project's Code of Conduct