Add kotlin native riegeli decompressor

[jononon]

While working on code for a different project, I needed to be able to decompress a Riegeli-compressed file in Kotlin.

My implementation follows the standards set forth in the specification: https://github.com/google/riegeli/blob/master/doc/riegeli_records_file_format.md

I do not plan on writing a compressor. Please let me know if you would like these submissions, otherwise I will incorporate them into our repositories directly.

Thanks so much!