Create Azure Speech to captions Filter

This filter uses the Azure Speech Services - Speech to captions feature to transcribe an audio
stream in real-time.

• Required for this filter is an Azure account with an Azure Speech service resource.
• Your own Azure speech service subscription key is required.
• This filter only works for Live Encodings.
• This filter transforms an audio input stream into a captions stream.
• The filter must be applied to a stream that has an audio input.
• The stream's codec configuration must be a subtitle or caption format (WebVtt, TTML, ..).