Add LUA linting and fix multiple errors

* Remove whitespaces
* Remove unused variables
* Remove unused arguments
* Fix syntax error

.luacheckrc

@@ -0,0 +1,23 @@
+compat = true
+allow_defined = true
+max_line_length = false
+
+read_globals = {
+    "GetAchievementId",
+    "GetAchievementCategoryInfo",
+    "GetAchievementCriterion",
+    "GetAchievementLink",
+    "GetAchievementNumCriteria",
+    "GetCategoryInfoFromAchievementId",
+    "GetCVar",
+    "GetNumAchievementCategories",
+    "GetPreviousAchievementInLine",
+    "CHAT_SYSTEM", 
+    "EVENT_ACHIEVEMENT_UPDATED",
+    "EVENT_ADD_ON_LOADED",
+    "EVENT_MANAGER", 
+    "LibStub",
+    "LINK_STYLE_BRACKET", 
+    "zo_callLater",
+    "ZO_SavedVars",
+}