docs: add a screenshot to README

Author: peterpeterparker

README.md

@@ -6,6 +6,12 @@ This code highlighter is developed with [Stencil](https://stenciljs.com) and use
 
 Furthermore, the inspiration for the design of the cards comes from the amazing [carbon](https://carbon.now.sh), a tool to create and share beautiful images of your source code.
 
+<div align="center">
+  <br>
+  <img src="static/screenshot.png" alt="Syntax highlighting code block as card" width="100%">
+  <br>
+</div>
+
 ## Table of contents
 
 - [Install](#install)