Add Target Action Support deprecation guide

Author: wagenet

content/ember/v6/deprecate-target-action-support.md

@@ -0,0 +1,61 @@
+---
+title: Deprecate Target Action Support
+until: 7.0.0
+since: 6.8.0
+---
+
+The `actions` hash on components, controllers, and routes, along with the `send` method, is deprecated. These APIs were primarily used with the now-deprecated `{{action}}` modifier and helper.
+
+The modern approach is to use standard class methods decorated with the `@action` decorator, and to pass functions directly.
+
+### `actions` hash and `send`
+
+**Old Pattern**
+
+Previously, you would define actions in an `actions` hash and use `this.send('actionName')` to call them.
+
+```javascript
+// app/components/my-component.js
+import Component from '@ember/component';
+
+export default Component.extend({
+  actions: {
+    save() {
+      // ... saving logic
+    },
+    cancel() {
+      // ... cancel logic
+    }
+  },
+
+  someMethod() {
+    this.send('save');
+  }
+});
+```
+
+**New Pattern**
+
+With modern classes, you can define methods directly on the class and decorate them with `@action`. You can then call them like any other method.
+
+```javascript
+// app/components/my-component.js
+import Component from '@glimmer/component';
+import { action } from '@ember/object';
+
+export default class MyComponent extends Component {
+  @action
+  save() {
+    // ... saving logic
+  }
+
+  @action
+  cancel() {
+    // ... cancel logic
+  }
+
+  someMethod() {
+    this.save();
+  }
+}
+```