brotli support

[szuecs]

#9 was closed by the issue creator and it seems that there is a working library that supports reader and writer for brotli https://github.com/andybalholm/brotli.

Any blockers in order to have this in this library, too?

[klauspost]

@szuecs Not as such, but I will likely have to do a complete rewrite for it to make sense to have here.

I don't just want to copy+paste code in here to have it here.