Add getAnsweredOffers API method for batch polling

Added RondevuAPI.getAnsweredOffers() and Rondevu.getAnsweredOffers()
methods to efficiently retrieve all answered offers with optional
timestamp filtering.

This enables offerers to poll for incoming connections in a single
request instead of polling each offer individually.

src/rondevu.ts

@@ -280,6 +280,22 @@ export class Rondevu {
         return await this.api.getOfferAnswer(serviceFqn, offerId)
     }
 
+    /**
+     * Get all answered offers (efficient batch polling for offerer)
+     * Returns all offers that have been answered since the given timestamp
+     */
+    async getAnsweredOffers(since?: number): Promise<{
+        offers: Array<{
+            offerId: string
+            serviceId?: string
+            answererId: string
+            sdp: string
+            answeredAt: number
+        }>
+    }> {
+        return await this.api.getAnsweredOffers(since)
+    }
+
     /**
      * Add ICE candidates to specific offer
      */