Adds aliasMethod deprecation

content/ember/v3/deprecate-alias-method.md

@@ -0,0 +1,55 @@
+---
+id: object.alias-method
+title: Deprecate `@ember/object#aliasMethod`
+until: '4.0.0'
+since: '3.8'
+---
+
+`@ember/object#aliasMethod` is a little known and rarely used method that allows
+user's to add aliases to objects defined with `EmberObject`:
+
+```js
+import EmberObject, { aliasMethod } from '@ember/object';
+
+export default EmberObject.extend({
+  foo: 123,
+  bar() {
+    console.log(this.foo);
+  },
+  baz: aliasMethod('bar'),
+});
+```
+
+This can be refactored into having one function call the other directly:
+
+```js
+import EmberObject from '@ember/object';
+
+export default EmberObject.extend({
+  foo: 123,
+  bar() {
+    console.log(this.foo);
+  },
+  baz() {
+    this.bar(...arguments);
+  },
+});
+```
+
+Avoid defining methods directly on the class definition, since this will not
+translate well into native class syntax in the future:
+
+```js
+// Do not use this, this is an antipattern! 🛑
+import EmberObject from '@ember/object';
+
+function logFoo() {
+  console.log(this.foo);
+}
+
+export default EmberObject.extend({
+  foo: 123,
+  bar: logFoo,
+  baz: logFoo,
+});
+```