fix(hermes): Retrieve `PublicKey` of a peer when creating SYN payload (#782)
* `pubsub_publish()` is now async * Fixes to async handling * `get_peer_identity()` is now async * Add code to call `hermes_ipfs_get_peer_identity` when creating SYN payload * Fix call to `_wait-for-athena-ready` * `hermes_ipfs_get_peer_identity` now accepts optional peer * Fix comment