[css-animations-2] Add issue about misplaced keyframes definitions

Author: birtles

css-animations-2/Overview.bs

@@ -379,6 +379,15 @@ its associated [=keyframes=] are generated as follows:
         and ordering them from earliest to latest,
         breaking ties by using the [=computed keyframe order=].
 
+    Issue: Any specific requirements on sorting computed keyframes introduced by
+    this spec should be integrated into
+    [[web-animations-1#calculating-computed-keyframes]].
+    Any specific requirements on used keyframes introduced by this spec
+    should be integrated into
+    [[web-animations-1#the-effect-value-of-a-keyframe-animation-effect]].
+    The above description of the distinction between these sets of keyframes
+    should be moved to an informative note.
+
     Note: Although the [=computed keyframe order=]
     sorts keyframes with <<percentage>> offsets,
     it maintains keyframes specified with a <<timeline-range-name>>