Add the on_page_change display trigger (#1687)

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

tests/test1.yaml

@@ -1874,6 +1874,12 @@ display:
       - id: page2
         lambda: |-
           // Nothing
+    on_page_change:
+      from: page1
+      to: page2
+      then:
+        lambda: |-
+          ESP_LOGD("display", "1 -> 2");
   - platform: ssd1306_spi
     model: 'SSD1306 128x64'
     cs_pin: GPIO23