Add --request-body and --curl flags

[twitchard]

Two changes

1. Fixes a bug where version was being supplied as null sometimes which is not actually accepted by the API.
2. Adds a --request-json flag that allows you to hardcode a json body to get sent. This is useful if you want to use multi-utterances or anything that the CLI doesn't fully support. You still get the audio played back, and you still get context parsed e.g. you can use --last in the next request if you want to use continuation.
3. Adds a --curl flag where you can use the CLI to construct a curl command that you can use by itself.