Update release notes

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -57,7 +57,13 @@
 ## Bug Fixes
 
 - 0W power requests are now not adjusted to exclusion bounds by the `PowerManager` and `PowerDistributor`, and are sent over to the microgrid API directly.
-- Fixed that `microgrid.frequency()` was sending `Quantity` objects instead of `Frequency`.
+
+- `microgrid.frequency()` / `GridFrequency`:
+
+  * Fix sent samples to use `Frequency` objects instead of raw `Quantity`.
+  * Handle `None` values in the received samples properly.
+  * Convert `nan` values in the received samples to `None`.
+
 - The resampler now properly handles sending zero values.
 
   A bug made the resampler interpret zero values as `None` when generating new samples, so if the result of the resampling is zero, the resampler would just produce `None` values.