fix some eslint rules

app/assets/javascripts/preview_markdown.js

-/* eslint-disable func-names, space-before-function-paren, no-var, one-var, one-var-declaration-per-line, wrap-iife, no-else-return, consistent-return, object-shorthand, comma-dangle, no-param-reassign, padded-blocks, camelcase, prefer-arrow-callback, max-len */
+/* eslint-disable func-names, no-var, one-var, one-var-declaration-per-line, object-shorthand, comma-dangle, prefer-arrow-callback, max-len */
 // MarkdownPreview
 //
@@ -76,7 +76,7 @@
     };
     return MarkdownPreview;
-  })();
+  }());
   markdownPreview = new window.MarkdownPreview();
@@ -151,5 +151,4 @@
     $form = $(this).closest('form');
     $(document).triggerHandler('markdown-preview:hide', [$form]);
   });
-
 }).call(this);