DOC: add some code comments

src/core/js/edit_mode.js

@@ -772,6 +772,8 @@ var edit_mode = new function () {
         header.children().remove();
         const form = $('<form class="form-horizontal"></form>').append(inputs);
         header.append(form);
+        // selectpicker is based on bootstrap-select and must be initializes
+        // AFTER it had been added to the dom tree.
         $(form).find(".selectpicker").selectpicker();
         edit_mode.add_parent_dropzone(entity);
 
@@ -1302,6 +1304,8 @@ var edit_mode = new function () {
         var inputs = edit_mode.create_value_inputs(property);
         editfield.children().remove();
         editfield.append(inputs);
+        // selectpicker is based on bootstrap-select and must be initializes
+        // AFTER it had been added to the dom tree.
         $(editfield).find(".selectpicker").selectpicker();
 
         // CHECKBOX `List [ ]`