Add support for Sensor state class (#1835)

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

esphome/components/template/sensor/__init__.py

@@ -7,8 +7,9 @@ from esphome.const import (
     CONF_LAMBDA,
     CONF_STATE,
     DEVICE_CLASS_EMPTY,
-    UNIT_EMPTY,
     ICON_EMPTY,
+    STATE_CLASS_NONE,
+    UNIT_EMPTY,
 )
 from .. import template_ns
 
@@ -17,7 +18,13 @@ TemplateSensor = template_ns.class_(
 )
 
 CONFIG_SCHEMA = (
-    sensor.sensor_schema(UNIT_EMPTY, ICON_EMPTY, 1, DEVICE_CLASS_EMPTY)
+    sensor.sensor_schema(
+        UNIT_EMPTY,
+        ICON_EMPTY,
+        1,
+        DEVICE_CLASS_EMPTY,
+        STATE_CLASS_NONE,
+    )
     .extend(
         {
             cv.GenerateID(): cv.declare_id(TemplateSensor),