Add scan interval information to README

To accompany PR rospogrigio/localtuya#549

README.md

@@ -44,6 +44,8 @@ localtuya:
     local_key: xxxxx
     friendly_name: Tuya Device
     protocol_version: "3.3"
+    scan_interval: # optional, only needed if energy monitoring values are not updating
+      seconds: 30 # Values less than 10 seconds may cause stability issues
     entities:
       - platform: binary_sensor
         friendly_name: Plug Status
@@ -112,9 +114,13 @@ select one of these, or manually input all the parameters.
 ![discovery](https://github.com/rospogrigio/localtuya-homeassistant/blob/master/img/1-discovery.png)
 
 If you have selected one entry, you only need to input the device's Friendly Name and the localKey.
+
+Setting the scan interval is optional, only needed if energy/power values are not updating frequently enough by default. Values less than 10 seconds may cause stability issues.
+
 Once you press "Submit", the connection is tested to check that everything works.
 
-![device](https://github.com/rospogrigio/localtuya-homeassistant/blob/master/img/2-device.png)
+![image](https://user-images.githubusercontent.com/1082213/146663895-41e1902b-4f09-4b21-b9d7-067d9cd67069.png)
+
 
 Then, it's time to add the entities: this step will take place several times. First, select the entity type from the drop-down menu to set it up.
 After you have defined all the needed entities, leave the "Do not add more entities" checkbox checked: this will complete the procedure.
@@ -140,6 +146,7 @@ You can obtain Energy monitoring (voltage, current) in two different ways:
   Note: Voltage and Consumption usually include the first decimal. You will need to scale the parament by 0.1 to get the correct values.
 1) Access the voltage/current/current_consumption attributes of a switch, and define template sensors
   Note:  these values are already divided by 10 for Voltage and Consumption
+1) On some devices, you may find that the energy values are not updating frequently enough by default. If so, set the scan interval (see above) to an appropriate value. Settings below 10 seconds may cause stability issues, 30 seconds is recommended.
 
 ```
        sensor: