Add Store extends EmberObject ember data deprecation

content/ember-data/v5/ember-data-deprecate-store-extends-ember-object.md

@@ -0,0 +1,31 @@
+---
+title: Store will no longer extend EmberObject in 6.0
+until: 6.0
+since: 5.4
+displayId: ember-data:deprecate-store-extends-ember-object
+---
+
+The Store class extending from EmberObject is deprecated and the class will no 
+longer extend from EmberObject in 6.0.
+
+Please remove usage of [EmberObject APIs](https://api.emberjs.com/ember/release/modules/@ember%2Fobject) 
+in your Store class.
+
+To mark the class as no longer extending from EmberObject, in ember-cli-build.js
+set the following config:
+
+```js
+const app = new EmberApp(defaults, {
+  emberData: {
+    deprecations: {
+      DEPRECATE_STORE_EXTENDS_EMBER_OBJECT: false
+    }
+ }
+});
+```
+
+If you are unsure whether your Store class uses EmberObject APIs, set this 
+config and uses of those APIs will throw exceptions. The most common API that 
+may have been used is `Store.extend({...`.
+
+This deprecation is from RFC [#1026](https://rfcs.emberjs.com/id/1026-ember-data-deprecate-store-extends-ember-object).