title: Google reCaptcha reset in TypeScript
body: <p>I'm developing Angular 2 + TypeScript app.
  I need to reset reCaptcha if form is invalid.
  But in my typescript code when I write <code>grecaptcha.reset();</code>, I get error: <code>Can not resolve symbol 'grecaptcha'</code> </p>
  
  <p>How can I reset reCaptcha or resolve/declare <code>grecaptcha</code> variable and where?</p>