rtic-sync: update CHANGELOG.md

Author: datdenkikniet

rtic-sync/CHANGELOG.md

@@ -8,6 +8,9 @@ For each category, _Added_, _Changed_, _Fixed_ add new entries at the top!
 ## [Unreleased]
 
 - Avoid a critical section when a `send`-link is popped and when returning `free_slot`.
+### Changed
+
+- Add `loom` support.
 - Don't force `Signal` import when using `make_signal` macro
 - Update `make_signal`'s documentation to match `make_channel`'s