ChaCha20-Poly1305 Cipher

Hi all,

I posted this question to GitHub as an issue but I'm reposing here in case
that was the wrong place to ask: https://github.com/bcgit/bc-java/issues/554

I see there's already implementations of ChaCha20 and Poly1305, as well as
an implementation of TlsAEADCipherImpl (BcChaCha20Poly1305) that brings
them together in the TLS module, but there doesn't seem to be a Cipher
instance available.

I know support for this is available in JDK 11 but I need access to it on
JDK 8 via BC provider for now.

Is this something that is planned or would you be open to a PR implementing
it?