Support Opus codec

[scharli]

Hi,

Thanks for the library, is there a plan to support Opus codec conversion like Vorbis is already in?
Maybe you can use https://github.com/google/opuscpp as single header dream

Thanks!

[julianstorer]

I'm unlikely to have time or reason to look at it in the near future, but it'd nice to have.

If you need it, you could always have a go yourself by following the pattern used for the other formats, and I'd be happy to help get it to a releasable state.

[scharli]

Thanks for quick response, I need to review and maybe I will try to implement