Adding badge for RBE workflow

[skip ci]

Author: diemol

README.md

@@ -1,6 +1,7 @@
 # Selenium
 
 [![CI](https://github.com/SeleniumHQ/selenium/actions/workflows/ci.yml/badge.svg?branch=trunk&event=schedule)](https://github.com/SeleniumHQ/selenium/actions/workflows/ci.yml)
+[![CI - RBE](https://github.com/SeleniumHQ/selenium/actions/workflows/ci-rbe.yml/badge.svg?branch=trunk&event=schedule)](https://github.com/SeleniumHQ/selenium/actions/workflows/ci-rbe.yml)
 [![Releases downloads](https://img.shields.io/github/downloads/SeleniumHQ/selenium/total.svg)](https://github.com/SeleniumHQ/selenium/releases)
 
 <a href="https://selenium.dev"><img src="common/images/selenium_logo_mark_green.svg" width="180" alt="Selenium Logo"/></a>