title: Create a transparent circle on top of an Overlay in react-native
body: <p><a href="https://i.stack.imgur.com/fi6iy.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fi6iy.png" alt="enter image description here"></a></p>
  
  <p>Source: <a href="https://github.com/amlcurran/ShowcaseView" rel="noreferrer">https://github.com/amlcurran/ShowcaseView</a>
  By checking source code, it has some <code>png</code>.</p>
  
  <p>Setting a backgroundColor <code>rgba(0, 0, 0, 0.8)</code> and creating a circle view on top of this simply doesn't work.</p>
  
  <p>How do I create an Overlay like this in react-native?</p>