shellcheck in workflow

.github/workflows/ci.yml

@@ -16,6 +16,8 @@ jobs:
         node-version: [10]
     steps:
       - uses: actions/checkout@v2
+      - run: apt-get install shellcheck -y
+      - run: ./shellcheck.sh
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v1
         with:
@@ -30,6 +32,8 @@ jobs:
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v2
+      - run: brew install shellcheck
+      - run: ./shellcheck.sh
       - run: brew install bats
       - run: ./dotbare finit -u https://github.com/kazhala/dotfiles.git
       - run: bats tests