Hello,
Please see the transcoding article below for the ingest and out bound streaming codecs that are supported followed by an article specific for WebM which has a preconfigured transcoding template that can be downloaded.
https://www.wowza.com/docs/how-to-set-up-and-run-wowza-transcoder-for-live-streaming
https://www.wowza.com/docs/how-to-transcode-live-streams-to-webm-for-mpeg-dash-playback
Please let me know if this will not meet the needs of your specific workflow.
Regards,
Jason Hatchett