Add firmware upload step to CI workflow

Added step to upload firmware artifact after build.

Author: alexanderlindquis

.github/workflows/Platformio_CI.yml

@@ -29,3 +29,9 @@ jobs:
           ln -s ~/.platformio/penv/bin/piodebuggdb /usr/local/bin/piodebuggdb
       - name: Build PlatformIO Project
         run: pio run
+
+      - name: Upload Firmware
+        uses: actions/upload-artifact@v4
+        with:
+          name: firmware
+          path: .pio/build/**/firmware.bin