Deno just copied documents from node, which has chacha20-poly1305 in createCipheriv, but it only support these ciphers:

https://github.com/denoland/deno/blob/main/ext/node/ops/crypto/cipher.rs#L22

Since RustCrypto already has chacha20poly1305, it should be not too difficult to add it.

I'm happy to contribute to deno, I'll appreciate it if anyone can help me.