Implement more dump_configs (#791)

esphome/components/dfplayer/dfplayer.h

@@ -52,6 +52,7 @@ class DFPlayer : public uart::UARTDevice, public Component {
   void random() { this->send_cmd_(0x18); }
 
   bool is_playing() { return is_playing_; }
+  void dump_config() override;
 
   void add_on_finished_playback_callback(std::function<void()> callback) {
     this->on_finished_playback_callback_.add(std::move(callback));