Feat/dictation endpoint (#32) Summary: Based on this request - https://github.com/wit-ai/wit-go/issues/31 1. Add new endpoint method 2. Add test .mp3 file for integration tests Pull Request resolved: https://github.com/wit-ai/wit-go/pull/32 Reviewed By: yuzh174 Differential Revision: D70269191 Pulled By: patapizza fbshipit-source-id: 1877424010543174a26cdf8976dba779df79abad