Added automation example for qrcode integration (#17677)

source/_integrations/qrcode.markdown

@@ -39,3 +39,22 @@ source:
       required: false
       type: string
 {% endconfiguration %}
+
+## Basic example
+
+An automation using this integration could look like this:
+
+```yaml
+automation:
+  - alias: "Catch QR code and arm the alarm system"
+    trigger:
+      - platform: state
+        entity_id: image_processing.qr_front_door
+        to: ARM_QR_CODE_VALUE
+    action:
+      - service: alarm_control_panel.alarm_arm_away
+        target:
+          entity_id: alarm_control_panel.home_alarm
+        data:
+          code: MY_ALARM_CODE
+```