title: ngx-translate with dynamic text on ts file
body: <p>I'm using <a href="https://ionicframework.com/docs/developer-resources/ng2-translate/" rel="noreferrer"><strong>ngx-translate</strong></a> for internationalization on <code>Ionic 3</code> app. I have used <code>pipe</code> nicely on <code>HTML</code> code. But now I have a situation like below on <code>ts</code> file. Can you tell me how to handle such dynamic use case with <code>ngx</code>?</p>
  
  <pre><code> updateApi(topic) {
       this.showToast(`Topic ${topic.name} subscribed!`);//this is the dynamic text
    }
  
   showToast(message) {
          let toast = this.toastCtrl.create({
              message: message,
              duration: 3000
          });
          toast.present();
      }
  </code></pre>
  
  <p>The problem here is I don't know the value of <code>${topic.name}</code> up front. So how can I give the <code>key/value</code> for that on <code>i18n</code> <code>json</code> file? or am I missing something here? </p>