Add documentation for faulty framesets

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/extractors/YoutubeStreamExtractor.java

@@ -1377,6 +1377,11 @@ public class YoutubeStreamExtractor extends StreamExtractor {
         return itagInfo;
     }
 
+    // Warning: When using this method be aware that the YouTube API very rarely returns framesets,
+    // that are slightly too small e.g. framesPerPageX = 5, frameWidth = 160, but the url contains
+    // a storyboard that is only 795 pixels wide (5*160 > 795). You will need to handle this
+    // "manually" to avoid errors.
+    // For further reference see: https://github.com/TeamNewPipe/NewPipe/pull/11596
     @Nonnull
     @Override
     public List<Frameset> getFrames() throws ExtractionException {