Add capabilities to modifier managers

Addresses deprecation `implicit-modifier-manager-capabilities`:
Custom modifier managers must define their capabilities using the
capabilities() helper function

Author: wongpeiyi

addon/modifier.js

@@ -0,0 +1,5 @@
+import Ember from 'ember';
+
+export const setModifierManager = Ember._setModifierManager;
+
+export const capabilities = Ember._modifierManagerCapabilities || (() => {});

addon/modifiers/did-insert.js

@@ -1,4 +1,4 @@
-import Ember from 'ember';
+import { setModifierManager, capabilities } from '../modifier';
 
 /**
   The `{{did-insert}}` element modifier is activated when an element is
@@ -44,8 +44,10 @@ import Ember from 'ember';
   @method did-insert
   @public
 */
-export default Ember._setModifierManager(
+export default setModifierManager(
   () => ({
+    capabilities: capabilities('3.13'),
+
     createModifier() {},
 
     installModifier(_state, element, args) {

addon/modifiers/did-update.js

@@ -1,4 +1,4 @@
-import Ember from 'ember';
+import { setModifierManager, capabilities } from '../modifier';
 
 /**
   The `{{did-update}}` element modifier is activated when any of its arguments
@@ -56,8 +56,10 @@ import Ember from 'ember';
   @method did-update
   @public
 */
-export default Ember._setModifierManager(
+export default setModifierManager(
   () => ({
+    capabilities: capabilities('3.13'),
+
     createModifier() {
       return { element: null };
     },

addon/modifiers/will-destroy.js

@@ -1,4 +1,4 @@
-import Ember from 'ember';
+import { setModifierManager, capabilities } from '../modifier';
 
 /**
   The `{{will-destroy}}` element modifier is activated immediately before the element
@@ -38,8 +38,10 @@ import Ember from 'ember';
   @method will-destroy
   @public
 */
-export default Ember._setModifierManager(
+export default setModifierManager(
   () => ({
+    capabilities: capabilities('3.13'),
+
     createModifier() {
       return { element: null };
     },