Add build step to CI

Author: cgewecke

.github/workflows/build.yml

@@ -21,6 +21,7 @@ jobs:
       - uses: actions/checkout@v2
       - run: npm install
       - run: npm run lint
+      - run: npm run build
       - run: npm run coverage
       - uses: coverallsapp/github-action@master
         with: