Replace datepicker with flatpicker

package.json

@@ -11,11 +11,12 @@
   },
   "dependencies": {
     "@fancyapps/fancybox": "^3.2.5",
-    "@fengyuanchen/datepicker": "^0.6.4",
+    "@fengyuanchen/datepicker": "^0.6.5",
     "bootstrap-sass": "^3.3.7",
     "bourbon": "^4.3.2",
     "cookieconsent": "^3.1.0",
     "dayjs": "^1.7.5",
+    "flatpickr": "^4.5.2",
     "font-awesome": "^4.7.0",
     "iframe-resizer": "^3.6.1",
     "jquery": "^2.2.4",