Add ability to steam audio as base64 encoded json

[Dyster2000]

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[Dyster2000]

This fixed a couple bugs.

1. In stream_function when it is parsing "start" parms, it checked if metadata was set, but then passes argv[2] to the is_valid_utf8() function, instead of [5] (or metadata).
2. I updated the AudioStreamer::isConnected() function as I found it started streaming the audio as soon as the WebSocketClient connected, so I was having multiple frames of audio written out before the send_initial_metadata() was called.

Then, per the title, I added the ability to send audio base64 encoded wrapped in json.

[amigniter]

Thank you for the PR and for identifying these issues.

The metadata argument bug was valid and has already been fixed separately.

For the other changes, I prefer to keep the current streaming behavior and audio format of the Community Edition, so I won't be adding the JSON/base64 audio streaming mode or merging the remaining changes from this PR.

Closing this PR, but thank you for the contribution and for reporting the metadata issue.