Decouple template from JS

Closes #3386957

• Define template
• Make new route for JS to get the rendered template
• Update JS

assets/language_suggestion.css

 #language-suggestion {
   position: absolute;
-  right: 20px;
   top: 20px;
+  right: 20px;
   display: none;
 }
 
 .ls-wrapper {
-  background-color: #fff;
-  border: 1px solid #c3c3c3;
   padding: 15px;
+  border: 1px solid #c3c3c3;
+  background-color: #fff;
   -webkit-box-shadow: 6px 8px 9px -10px black;
-     -moz-box-shadow: 6px 8px 9px -10px black;
-          box-shadow: 6px 8px 9px -10px black;
+  -moz-box-shadow: 6px 8px 9px -10px black;
+  box-shadow: 6px 8px 9px -10px black;
 }
 
 .ls-wrapper .ls-message,