refactor: Use ember-cli-babel-plugin-helpers

Also update addon's ember-cli-babel version to latest

index.js

@@ -1,31 +1,22 @@
 'use strict';
 
 const { resolve } = require('path');
+const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
 
 module.exports = {
   name: require('./package').name,
 
   included() {
     this._super.included.apply(this, arguments);
 
-    this.patchEmberModulesAPIPolyfill();
+    this.addBabelPlugin();
   },
 
-  patchEmberModulesAPIPolyfill() {
-    const babel = this.parent.findOwnAddonByName
-      ? this.parent.findOwnAddonByName('ember-cli-babel') // parent is an addon
-      : this.parent.findAddonByName('ember-cli-babel'); // parent is an app
+  addBabelPlugin() {
+    let app = this._findHost();
 
-    if (babel.__CachedDecoratorPolyfillApplied) return;
-    babel.__CachedDecoratorPolyfillApplied = true;
-
-    const { _getEmberModulesAPIPolyfill } = babel;
-
-    babel._getEmberModulesAPIPolyfill = function (...args) {
-      const plugins = _getEmberModulesAPIPolyfill.apply(this, args);
-      if (!plugins) return;
-
-      return [[resolve(__dirname, './lib/transpile-modules.js')], ...plugins];
-    };
+    if (!hasPlugin(app, 'ember-cache-decorator-polyfill')) {
+      addPlugin(app, resolve(__dirname, './lib/transpile-modules.js'));
+    }
   }
 };

package.json

@@ -41,7 +41,8 @@
   "dependencies": {
     "@glimmer/tracking": "^1.0.4",
     "ember-cache-primitive-polyfill": "^1.0.1",
-    "ember-cli-babel": "^7.21.0"
+    "ember-cli-babel": "^7.21.0",
+    "ember-cli-babel-plugin-helpers": "^1.1.1"
   },
   "devDependencies": {
     "@ember/optional-features": "^2.0.0",