Add device class support to text sensor (#6202)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/components/api/api.proto

@@ -600,6 +600,7 @@ message ListEntitiesTextSensorResponse {
   string icon = 5;
   bool disabled_by_default = 6;
   EntityCategory entity_category = 7;
+  string device_class = 8;
 }
 message TextSensorStateResponse {
   option (id) = 27;