Merge pull request #520 from grafana/docs/add-mp4-readme

docs: update README to include an mp4 video

Author: mdcruz

README.md

@@ -24,6 +24,8 @@
 
 **xk6-browser** is a [k6](https://k6.io/) extension adding support for automation of browsers via the [Chrome Devtools Protocol](https://chromedevtools.github.io/devtools-protocol/) (CDP).
 
+https://user-images.githubusercontent.com/10811379/188889687-660ce8f9-264d-4dd0-905c-41a909102be8.mp4
+
 Special acknowledgment to the authors of [Playwright](https://playwright.dev/) and [Puppeteer](https://github.com/puppeteer/puppeteer) for their trailblazing work in this area. This project is heavily influenced and in some regards based on the code of those projects.
 
 ## Goals