Compatibility Issue with Ember.js 5.x - `htmlSafe` Not Implemented in `@ember/string`

Hi, I've encountered an issue when using the `ember-burger-menu` package with Ember.js 5.x. Upon trying to run the application, the following error appears in the browser console:

```js
Uncaught (in promise) Error: htmlSafe is not implemented in the `@ember/string` package. Please import from `@ember/template` instead.
```

It seems like `htmlSafe` is being imported from `@ember/string`, which is no longer supported in Ember.js 5.x. The correct import should be from `@ember/template`.