CI: add compile example check using latest released portenta core

Author: pennam

.github/workflows/compile-examples.yml

@@ -56,6 +56,8 @@ jobs:
             platform-name: arduino:samd
           - fqbn: "arduino:mbed:envie_m7"
             platform-name: arduino:mbed
+          - fqbn: "arduino:mbed_portenta:envie_m7"
+            platform-name: arduino:mbed_portenta
           - fqbn: "esp8266:esp8266:huzzah"
             platform-name: esp8266:esp8266
           - fqbn: "esp32:esp32:esp32"