introduce nip42 and public/personal usage

Signed-off-by: Yonle <yonle@lecturify.net>

nip42.js

@@ -0,0 +1,19 @@
+const { getEventHash, getSignature } = require("nostr-tools");
+
+module.exports = (relay, pubkey, privkey, challenge) => {
+  if (!privkey) return;
+  let signed_challenge = {
+    pubkey,
+    created_at: Math.floor(Date.now() / 1000),
+    kind: 22242,
+    tags: [
+      ["relay", relay.url],
+      ["challenge", challenge]
+    ],
+    content: ""
+  }
+
+  signed_challenge.id = getEventHash(signed_challenge);
+  signed_challenge.sig = getSignature(signed_challenge, privkey);
+  relay.send(JSON.stringify(["AUTH", signed_challenge]));
+}