Add midi-rainbow noteskin

NoteSkins/dance/midi-rainbow/Down Tap Note.lua

@@ -0,0 +1,8 @@
+return Def.Sprite {
+	Texture=NOTESKIN:GetPath( '_down', 'tap note' );
+	Frames = Sprite.LinearFrames( 4, 1 );
+	InitCommand=cmd(setstate,2);
+	DrawTapNoteMessageCommand=function(self,parent)
+		parent:spin();
+	end;
+};

NoteSkins/dance/midi-rainbow/metrics.ini

@@ -0,0 +1,7 @@
+[Global]
+FallbackNoteSkin=midi-solo
+
+[NoteDisplay]
+TapNoteNoteColorType=ProgressAlternate
+TapNoteNoteColorCount=4
+TapNoteNoteColorTextureCoordSpacingY=0.25