nostr package: vastly simplify the API (#412)

* vastly simplify the api

* add missing await

* add eose to emitter

* add eose to conn

* add eose to the client

* eose test

* improve test suite, add dm tests

* demonstrate that nostr-rs-relay auth options don't work

* readme files

* cleanup

* fetch relay info

* test readyState

* export fetchRelayInfo

* cleanup

* better async/await linting

* use strictEqual in tests

* additional eslint rules

* allow arbitrary extensions

* saner error handling

* update README

* implement nip-02

---------

Co-authored-by: Kieran <kieran@harkin.me>

packages/nostr/src/common.ts

@@ -0,0 +1,42 @@
+/**
+ * A UNIX timestamp.
+ */
+export type Timestamp = number
+
+/**
+ * Calculate the unix timestamp (seconds since epoch) of the `Date`. If no date is specified,
+ * return the current unix timestamp.
+ */
+export function unixTimestamp(date?: Date): Timestamp {
+  return Math.floor((date ?? new Date()).getTime() / 1000)
+}
+
+/**
+ * Throw if the parameter is null or undefined. Return the parameter otherwise.
+ */
+export function defined<T>(v: T | undefined | null): T {
+  if (v === undefined || v === null) {
+    throw new NostrError("bug: unexpected undefined")
+  }
+  return v
+}
+
+/**
+ * Parse the JSON and throw a @see {@link NostrError} in case of error.
+ */
+export function parseJson(data: string) {
+  try {
+    return JSON.parse(data)
+  } catch (e) {
+    throw new NostrError(`invalid json: ${e}: ${data}`)
+  }
+}
+
+/**
+ * The error thrown by this library.
+ */
+export class NostrError extends Error {
+  constructor(message?: string) {
+    super(message)
+  }
+}