Document IR diagnostics cleanup

Signed-off-by: Cristiano Calcagno <cristianoc@users.noreply.github.com>

Author: cristianoc

CHANGELOG.md

@@ -34,6 +34,7 @@
 #### :house: Internal
 
 - Add the `-check-lam` compiler option, enable Lambda invariant checking in compiler tests, and remove build-profile-dependent checking. https://github.com/rescript-lang/rescript/pull/8534
+- Replace `-bs-diagnose` with `-debug-ir` and make IR diagnostic artifacts deterministic, compilation-local, and easy to clean. https://github.com/rescript-lang/rescript/pull/8535
 
 # 13.0.0-alpha.5