Add BASE_URL constant to page and have AJAX calls use it

resources/views/admin/airports/script.blade.php

@@ -1,5 +1,16 @@
 @section('scripts')
 <script>
+function phpvms_vacentral_airport_lookup(icao, callback) {
+    $.ajax({
+        url: BASE_URL + '/api/airports/'+ icao + '/lookup',
+        method: 'GET',
+        headers: {
+            'x-api-key': PHPVMS_USER_API_KEY
+        }
+    }).done(function (data, status) {
+        callback(data.data);
+    });
+}
 
 $(document).ready(function() {