added a dedicated platform install step in every library CI

Author: zekageri

.github/workflows/ci.yml

@@ -34,6 +34,9 @@ jobs:
       - name: Install PIOArduino Core
         run: python -m pip install --upgrade https://github.com/pioarduino/platformio-core/archive/refs/tags/v6.1.18.zip
 
+      - name: Install PIOArduino ESP32 Platform
+        run: pio platform install https://github.com/pioarduino/platform-espressif32.git
+
       - name: Build library examples (ESP32 Arduino)
         run: |
           set -e