audioreactive effect improvements

- Info Page: add a small horizontal line below usermod specific part. Improves readability.
- updated 2D mapping mode of some  1D soundreactive effects
- alllow some effects to fade slowly, even slower that possible with SEGMENT.fade_out(). Looks nice.

not sure why - most effects only fade when using SEGMENT.fade_out(), while some need SEGMENT.fadeToBlackBy().

usermods/audioreactive/audio_reactive.h

@@ -1317,6 +1317,10 @@ class AudioReactive : public Usermod {
         infoArr.add(fftTime-sampleTime);
         infoArr.add("ms");
         #endif
+
+        // add a small horizontal line, for better readability
+        infoArr = user.createNestedArray(F("<hr style=\"height:1px;border-width:0;color:gray;background-color:gray\" />"));
+        infoArr.add(F(" <hr style=\"height:1px;border-width:0;color:gray;background-color:gray\" /> "));
       }
     }