Use webpack to deliver newest ACE editor

With this commit, we change the delivery method for the ACE editor from manually copied files to using yarn and webpack. As a side-change, we also modify how the mode is selected through JavaScript instead of Ruby.

Through webpack, the `modePath`, `themePath`, and `workerPath` are automatically determined and working as expected.

Closes #250

app/assets/javascripts/community_solution.js

@@ -4,7 +4,6 @@ $(document).on('turbolinks:load', function() {
         CodeOceanEditor.sendEvents = false;
         CodeOceanEditor.editors = [];
         CodeOceanEditor.initializeDescriptionToggle();
-        CodeOceanEditor.configureEditors();
         CodeOceanEditor.initializeEditors();
         CodeOceanEditor.initializeEditors(true);
         CodeOceanEditor.initializeFileTree();