* Updated DocumentConverter interface
* Updated all DocumentConverter classes
* Added support for various new audio files.
* Updated sample plugin to new DocumentConverter interface.
* Updated project README with notes about changes, and use-cases.
* Updated DocumentConverter documentation.
* Move priority to outside DocumentConverter, allowing them to be reprioritized, and keeping the DocumentConverter interface simple.
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Co-authored-by: Kenny Zhang <kzhang678@gmail.com>
