Adding Amplify Support for Transcribe Streaming of Amazon Transcribe

**Is your feature request related to a problem? Please describe.**
- This isn't a problem in itself, but I've got customer wanting this feature and the docs are a bit confusing about if Transcribe Streaming is supported or not.

**Describe the solution you'd like**
- AWS Amplify is already using Amazon Transcribe.
- We need to create a new API for it, and it will need to return a stream not promise (This is how the current API works).

**Describe alternatives you've considered**
- There are no alternatives for this at the moment

Start by locating the existing Amazon Transcribe integration and its API documentation, then determine how the requested streaming API relates to the current promise-based API. Done means the supported Transcribe Streaming behavior and the required new API are clearly defined and documented.

Written by the indexing model from the issue text.