Finish pass on docs

docs/util/nip42.md

@@ -0,0 +1,30 @@
+# NIP-42
+
+Utilities for NIP-42 relay authentication, allowing clients to authenticate with relays that require it.
+
+## Functions
+
+### makeRelayAuth(url, challenge)
+
+Creates a CLIENT_AUTH event (kind 22242) for relay authentication as specified in NIP-42.
+
+**Parameters:**
+- `url` - The relay URL to authenticate with
+- `challenge` - The challenge string provided by the relay
+
+**Returns:** Unsigned event object with relay and challenge tags
+
+## Example
+
+```typescript
+import {makeRelayAuth} from "@welshman/util"
+
+// Create auth event when relay sends AUTH challenge
+const authEvent = makeRelayAuth(
+  "wss://relay.example.com",
+  "challenge-string-from-relay"
+)
+
+// Sign the event with your signer
+const signedAuth = await signer.sign(authEvent)
+```