Add formatters module that contains a few basic built-in formatters for JSON, SRT, and an arbitrary plain TEXT. Mainly for examples of implementing your own.
Module contains an abstract base class `TranscriptFormatter` so that anyone can create their own TranscriptFormatter class
Module contains at runtime a `formats` which is basically an instance of a factory of classes (not sure if that is the correct term to use). But it itself is an instance that folks can add custom formatter classes that the API can make use of.
Chris Howell