fix(back-button): subscribe to body

angular/src/providers/nav-controller.ts

@@ -21,7 +21,7 @@ export class NavController {
     private location: Location,
     @Optional() private router?: Router
   ) {
-    window && window.addEventListener('ionBackButton', (ev) => {
+    window && window.document.body.addEventListener('ionBackButton', (ev) => {
       (ev as BackButtonEvent).detail.register(0, () => this.goBack());
     });
   }

core/package.json

@@ -21,7 +21,8 @@
   "unpkg": "dist/ionic.js",
   "files": [
     "dist/",
-    "css/"
+    "css/",
+    "loader/"
   ],
   "dependencies": {
     "ionicons": "4.4.3"

core/src/utils/hardware-back-button.ts

@@ -23,7 +23,7 @@ export function startHardwareBackButton(win: Window) {
         }
       }
     });
-    win.dispatchEvent(ev);
+    win.document.body.dispatchEvent(ev);
 
     if (handlers.length > 0) {
       let selectedPriority = Number.MIN_SAFE_INTEGER;