fix: connection issues with Firefox

This adds Hyper, and a 200 response code.  Prior to this, Firefox
would fail to connect.  There is also a text document displayed at the
root URL to indicate this is a Nostr relay.

Fixes https://todo.sr.ht/~gheartsfield/nostr-rs-relay/15

Cargo.toml

@@ -23,3 +23,4 @@ rusqlite = "^0.26"
 lazy_static = "^1.4"
 governor = "^0.4"
 nonzero_ext = "^0.3"
+hyper={ version="0.14", features=["server","http1","http2","tcp"] }