docs: Add video tutorial

Author: bennycode

README.md

@@ -13,3 +13,9 @@ Send messages to Wire conversations using GitHub Actions.
       conversation: ${{secrets.WIRE_CONVERSATION}}
       text: 'Hello, World!'
 ```
+
+## Tutorial
+
+Click the thumbnail if you want to watch our setup video:
+
+[![Click to watch](https://img.youtube.com/vi/1OebjwY6sXk/0.jpg)](https://www.youtube.com/watch?v=1OebjwY6sXk)