Add rolling badge (#323)

Signed-off-by: Felipe Balbi <febalbi@microsoft.com>
Co-authored-by: Felipe Balbi <febalbi@microsoft.com>

Author: felipebalbi

README.md

@@ -1,5 +1,6 @@
 [![check](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/check.yml/badge.svg)](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/check.yml)
 [![no-std](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/nostd.yml/badge.svg)](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/nostd.yml)
+[![rolling](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/rolling.yml/badge.svg)](https://github.com/OpenDevicePartnership/embedded-services/actions/workflows/rolling.yml)
 [![LICENSE](https://img.shields.io/badge/License-MIT-blue)](./LICENSE)
 
 # EC Services