Merge pull request #1584 from ethereum-optimism/maurelian/eng-1528-fa…

…il-ci-on-yarn-lock-changes

Check in yarn.lock, and fail if yarn install changes lock file

.github/workflows/ts-packages.yml

@@ -43,6 +43,9 @@ jobs:
         # if: steps.yarn-cache.outputs.cache-hit != 'true'
         run: yarn install
 
+      - name: Check yarn.lock for changes
+        run: git diff --exit-code
+
       - name: Build
         run: yarn build