Add kOfxImageEffectPropUniqueIdentifier to release notes

Signed-off-by: Greg Cotten <[email protected]>

Author: gregcotten

release-notes.md

@@ -24,6 +24,7 @@ This is version 1.6 of the OpenFX API.
 ## Detailed List of Changes
 
 - Add `kOfxImageEffectPropNoSpatialAwareness`. Allows the host and plugin to coordinate a render that ensures no spatial changes to the image.
+- Add `kOfxImageEffectPropUniqueIdentifier`. Allows the plugin to differentiate its instances (e.g. for stably seeding a random number generator per-instance).
 
 # Release Notes - 1.5