[STM32] Add stm32 CI link to readme build list (#29413)

* add link stm32 ci in core readme

* Restyled by prettier-markdown

---------

Co-authored-by: Restyled.io <commits@restyled.io>

README.md

@@ -24,12 +24,12 @@
 [![nRF Connect SDK](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20nRF%20Connect%20SDK/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-nrfconnect.yaml)
 [![Open IoT SDK](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20Open%20IoT%20SDK/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-openiotsdk.yaml)
 [![QPG](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20QPG/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-qpg.yaml)
+[![STM32](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20stm32/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-stm32.yaml)
 [![Telink](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20Telink/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-telink.yaml)
 [![Tizen](https://github.com/project-chip/connectedhomeip/workflows/Build%20example%20-%20Tizen/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/examples-tizen.yaml)
 
 **Tests**
 
-
 [![Unit / Integration Tests](https://github.com/project-chip/connectedhomeip/workflows/Unit%20/%20Integration%20Tests/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/unit_integration_test.yaml)
 [![Cirque](https://github.com/project-chip/connectedhomeip/workflows/Cirque/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/cirque.yaml)
 [![QEMU](https://github.com/project-chip/connectedhomeip/workflows/QEMU/badge.svg)](https://github.com/project-chip/connectedhomeip/actions/workflows/qemu.yaml)