feat(ffi): Add fn RoomPowerLevels::events

With this we can query the power level value for any event type

bindings/matrix-sdk-ffi/src/room/power_levels.rs

@@ -29,6 +29,10 @@ impl RoomPowerLevels {
         self.inner.clone().into()
     }
 
+    fn events(&self) -> HashMap<String, i64> {
+        self.inner.events.iter().map(|(key, value)| (key.to_string(), (*value).into())).collect()
+    }
+
     /// Gets a map with the `UserId` of users with power levels other than `0`
     /// and their power level.
     pub fn user_power_levels(&self) -> HashMap<String, i64> {