TrackQueue: Add current_queue method (#16)

src/tracks/queue.rs

@@ -278,6 +278,19 @@ impl TrackQueue {
 
         inner.stop_current()
     }
+
+    /// Returns a list of currently queued tracks.
+    ///
+    /// Does not allow for modification of the queue, instead returns a snapshot of the queue at the time of calling.
+    ///
+    /// Use [`modify_queue`] for direct modification of the queue.
+    ///
+    /// [`modify_queue`]: #method.modify_queue
+    pub fn current_queue(&self) -> Vec<TrackHandle> {
+        let inner = self.inner.lock();
+
+        inner.tracks.iter().map(|q| q.handle()).collect()
+    }
 }
 
 impl TrackQueueCore {