Add coordinator example for PARALLEL_UPDATES in IQS (#2482)

Author: epenet

docs/core/integration-quality-scale/rules/parallel-updates.md

@@ -31,13 +31,27 @@ class MySensor(SensorEntity):
 
 :::info
 When using a coordinator, you are already centralizing the data updates.
-This means that usually only the action calls will be relevant to consider for setting the number of parallel updates.
+This means you can set `PARALLEL_UPDATES = 0` for read-only platforms (`binary_sensor`, `sensor`, `device_tracker`, `event`)
+and only the action calls will be relevant to consider for setting an appropriate number of parallel updates.
 :::
 
+`sensor.py`
+```python {1,2} showLineNumbers
+# Coordinator is used to centralize the data updates
+PARALLEL_UPDATES = 0
+
+class MySensor(CoordinatorEntity, SensorEntity):
+    """Representation of a sensor."""
+
+    def __init__(self, device: Device) -> None:
+        """Initialize the sensor."""
+        ...
+```
+
 ## Additional resources
 
 For more information about request parallelism, check the [documentation](/docs/integration_fetching_data#request-parallelism) for it.
 
 ## Exceptions
 
-There are no exceptions to this rule.
+There are no exceptions to this rule.