Form: add select2 form multiple select

app/assets/javascripts/new_design/application.js

@@ -17,4 +17,5 @@
 //= require leaflet.1.1.0
 //= require highcharts
 //= require chartkick
+//= require select2
 //= require_tree .

app/assets/javascripts/new_design/champs/multiple_drop_down_list.js

@@ -0,0 +1,3 @@
+document.addEventListener('turbolinks:load', function() {
+  $('select.select2').select2();
+});