Update Hydroquebec for multi contracts accounts (#2191)

source/_components/sensor.hydroquebec.markdown

@@ -16,12 +16,18 @@ ha_iot_class: "Cloud Polling"
 
 Integrate your [Hydro-Québec](https://www.hydroquebec.com/portail/) consumption profile information into Home Assistant.
 
+<p class='note warning'>
+Breaking change: Since Home Assistant v0.40,
+**contract** attribute is required.
+</p>
+
 ```yaml
 # Example configuration.yaml entry
 sensor:
   - platform: hydroquebec
     username: MYUSERNAME
     password: MYPASSWORD
+    contract: 123456789
     monitored_variables:
      - period_total_bill
      - period_length
@@ -38,8 +44,9 @@ sensor:
 
 Configuration variables:
 
-- **username** (*Required*): The App Token for your account.
-- **password** (*Required*): The App Token for your account.
+- **username** (*Required*): Your Hydro-Québec Username
+- **password** (*Required*): Your Hydro-Québec Password
+- **contract** (*Required*): Your Hydro-Québec Contract
 - **monitored_variables** array (*Required*): Variables to monitor.
   - **period_total_bill** : Current period bill
   - **period_length**: Current period length
@@ -52,3 +59,13 @@ Configuration variables:
   - **yesterday_total_consumption**: Yesterday total consumption
   - **yesterday_lower_price_consumption**: Yesterday lower price consumption
   - **yesterday_higher_price_consumption**: Yesterday higher price consumption
+
+To find your contract id, go to the [Hydro-Québec website](https://www.hydroquebec.com/portail/)
+and connect to your account.
+On the main page your can see your contract IDs.
+It should be something like: "Contract 1234 56789".
+You just have to keep numbers and remove the space.
+
+<p class='note warning'>
+Multi contracts accounts are supported only from Home Assistant v0.40.
+</p>