checkout submodules

Author: chrisirhc

.github/workflows/ci.yml

@@ -6,7 +6,10 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - name: Checkout repository and submodules
+      uses: actions/checkout@v3
+      with:
+        submodules: true
 
     - name: Add vendored flutter to PATH
       run: |