fetch submodules

.github/workflows/build.yml

@@ -28,6 +28,9 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v3
 
+    - name: Checkout submodules
+      run: git submodule update --init --depth 1 certificates
+
     - name: Build
       run: docker run --rm -v $PWD:/project -w /project espressif/idf:v3.3.1 make firmware