Add update APIs for Calendar Entities (home-assistant#1590)

Author: allenporter

docs/core/entity/calendar.md

@@ -35,6 +35,7 @@ and are combined using the bitwise or (`|`) operator.
 | ------------------- | ------------------------------------------------------------------ |
 | `CREATE_EVENT`      | Entity implements the methods to allow creation of events.  |
 | `DELETE_EVENT`      | Entity implements the methods to allow deletion of events.  |
+| `UPDATE_EVENT`      | Entity implements the methods to allow update of events.  |
 
 
 ## Methods
@@ -92,6 +93,29 @@ class MyCalendar(CalendarEntity):
         """Delete an event on the calendar."""
 ```
 
+### Update Events
+
+A calendar entity may support deleting events by specifying the `UPDATE_EVENT` supported feature. Integrations that support mutation must support rfc5545 recurring events.
+
+There are three ways that recurring events may be deleted:
+- Specifying only the `uid` will update the entire series
+- Specifying the `uid` and `recurrence_id` will update the specific event instance in the series
+- Specifying `uid`, `recurrence_id`, and a `recurrence_range` value may update a range of events starting at `recurrence_id`. Currently rfc5545 allows the [range](https://www.rfc-editor.org/rfc/rfc5545#section-3.2.13) value of `THISANDFUTURE`.
+
+```python
+class MyCalendar(CalendarEntity):
+
+    async def async_update_event(
+        self,
+        uid: str,
+        event: dict[str, Any],
+        recurrence_id: str | None = None,
+        recurrence_range: str | None = None,
+    ) -> None:
+        """Delete an event on the calendar."""
+```
+
+
 ## CalendarEvent
 
 A `CalendarEvent` represents an individual event on a calendar.