add CurrentNoteSkin luathreadvariable for noteskins

somehow you cant really get the current noteskin name without looking at player options which isnt ideal so hand it via the loader which is usually accurate

src/Etterna/Singletons/NoteSkinManager.cpp

@@ -581,6 +581,7 @@ NoteSkinManager::PushActorTemplate(Lua* L,
 	LuaThreadVariable varSpriteOnly("SpriteOnly",
 									LuaReference::Create(bSpriteOnly));
 	LuaThreadVariable varColor("Color", Color);
+	LuaThreadVariable varNoteskinName("CurrentNoteSkin", m_sCurrentNoteSkin);
 
 	if (data.m_Loader.IsNil()) {
 		LuaHelpers::ReportScriptError("No loader for noteskin!",