Memorelay: add supportedNips property

src/storages/memorelay.ts

@@ -10,6 +10,11 @@ class Memorelay implements EventStore {
     this.#cache = new LRUCache<string, Event>(...args);
   }
 
+  /** NIPs supported by this storage method. */
+  get supportedNips(): number[] {
+    return [1];
+  }
+
   /** Iterate stored events. */
   *#events(): Generator<Event> {
     for (const event of this.#cache.values()) {