ember-bootstrap + ember-autoresize

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: "Ember\nTwiddle",
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>


{{#bs-form model=this as |form|}}
  {{#form.element label="Description" placeholder="Enter description..." property="appName" as |el|}}
  	{{textarea autoresize=true value=el.value}}
  {{/form.element}}
{{/bs-form}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "^3.10",
    "ember-template-compiler": "^3.10",
    "ember-testing": "^3.10"
  },
  "addons": {
    "ember-bootstrap": "^4.0.0",
    "ember-autoresize": "1.3.2"
  }
}