scripts+GitHub: check submodule version bump

.github/workflows/main.yml

@@ -104,6 +104,29 @@ jobs:
       - name: check commits
         run: scripts/check-each-commit.sh upstream/master
 
+  ########################
+  # check submodules
+  ########################
+  check-submodules:
+    name: check submodules
+    runs-on: ubuntu-latest
+    steps:
+      - name: git checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: fetch and rebase on master
+        run: |
+          git remote add upstream https://github.com/lightningnetwork/lnd
+          git fetch upstream
+          export GIT_COMMITTER_EMAIL="lnd-ci@example.com"
+          export GIT_COMMITTER_NAME="LND CI"
+          git rebase upstream/master
+
+      - name: check submodules
+        run: scripts/check-submodule-version.sh upstream/master
+
   ########################
   # lint code
   ########################