Add testing suggestion

Author: alexsapps

README.md

@@ -5,3 +5,10 @@
 2. Edit scripts in **src** directory.
 3. Run ```npm run build``` to build locally.
 3. Push to master to automatically build & deploy changes to S3.
+
+## Testing
+
+The easiest way to test changes may be this:
+
+Duplicate the "Events" page on Webflow, paste the script contents into a
+`<script>` tag on the page, and then delete the test page when done.