Add screenshots

README.md

@@ -4,8 +4,13 @@ widgets used for quizzes.
 
 ## Available widgets
 - [Fill-in-the-gaps text (selector)](src/widgets/gapfill-select.js)
+
+![Screenshot of gapfill-select widget](screenshots/gapfill-select.png)
+
 - [Fill-in-the-gaps text (open input)](src/widgets/gapfill-open.js)
 
+![Screenshot of gapfill-select widget](screenshots/gapfill-open.png)
+
 ## Usage
 Each widget is its standalone file in [`src/widgets`](src/widgets), as a
 JavaScript [module](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules).