Added eslint. To lint, npm run lint.

Linted the entire project. Using different rules for the script files
as there are a lot of undefined variables just because of the way the
DOM's global scope works.

Mostly just code cleanup, however the linter did catch a minor bug with
a settings regex. That has been corrected.

app/assets/js/configmanager.js

@@ -73,7 +73,7 @@ const DEFAULT_CONFIG = {
     modConfigurations: []
 }
 
-let config = null;
+let config = null
 
 // Persistance Utility Functions