Implement passthroughAll to make it easier for adding things to the end of a packet.

src/main/java/us/myles/ViaVersion/api/PacketWrapper.java

@@ -163,6 +163,21 @@ public class PacketWrapper {
         return value;
     }
 
+    /**
+     * Take all the inputs and write them to the output.
+     *
+     * @throws Exception If it failed to read or write
+     */
+    public void passthroughAll() throws Exception {
+        // Copy previous objects
+        packetValues.addAll(readableObjects);
+        readableObjects.clear();
+        // If the buffer has readable bytes, copy them.
+        if(inputBuffer.readableBytes() > 0){
+            read(Type.REMAINING_BYTES);
+        }
+    }
+
     /**
      * Write the current output to a buffer.
      *