Added passthrough of allowOutsideClick to focus-trap

refs mainmatter#435
refs mainmatter#295

https://github.com/focus-trap/focus-trap is used internally for keeping focus inside a modal and for clicks outside to close the modal. It's `clickOutsideDecactivates` config is exposed allowing for  clicks on wormholed elements such as dropdowns inside a modal to not close the modal unexpectedly, however without the companion `allowOutsideClick` config those clicks are prevented from performing any interaction.

- added `allowOutsideClick` to the options passed through from the `modals` service to the `focus-trap` initialisation

README.md

@@ -1,2 +1,5 @@
 Forked from https://github.com/simplabs/ember-promise-modals with specific changes for https://github.com/TryGhost/Admin.
 Not recommended for general use, this package will be removed if upstream becomes compatible with our requirements.
+
+Custom changes:
+- added `allowOutsideClick` passthrough from the `modals` service to the `focus-trap` initialisation so `clickOutsideDeactivates` and `allowOutsideClick` and be used in tandem to allow wormholed content such as dropdowns to work inside of a modal

addon/components/modal.js

@@ -30,9 +30,10 @@ export default Component.extend({
   didInsertElement() {
     this._super(...arguments);
 
-    let { clickOutsideDeactivates } = this.modals;
+    let { allowOutsideClick, clickOutsideDeactivates } = this.modals;
     let element = document.getElementById(this.modalElementId);
     let options = {
+      allowOutsideClick,
       clickOutsideDeactivates,
       fallbackFocus: `#${this.modalElementId}`,
       onDeactivate: () => {

addon/services/modals.js

@@ -11,6 +11,7 @@ export default Service.extend({
   }),
   top: alias('_stack.lastObject'),
 
+  allowOutsideClick: undefined,
   clickOutsideDeactivates: true,
 
   init() {