Add select entities and implement template select (#2067)

Co-authored-by: Otto Winter <otto@otto-winter.com>

esphome/core/controller.cpp

@@ -59,6 +59,12 @@ void Controller::setup_controller() {
       obj->add_on_state_callback([this, obj](float state) { this->on_number_update(obj, state); });
   }
 #endif
+#ifdef USE_SELECT
+  for (auto *obj : App.get_selects()) {
+    if (!obj->is_internal())
+      obj->add_on_state_callback([this, obj](const std::string &state) { this->on_select_update(obj, state); });
+  }
+#endif
 }
 
 }  // namespace esphome