adding CI for shellcheck

Author: asere

.github/workflows/shellcheck-action.yml

@@ -0,0 +1,28 @@
+# This is a basic workflow to help you get started with Actions
+name: CI shellcheck
+
+# Controls when the action will run.
+on:
+  # Triggers the workflow pull request events but only for the master branch
+  pull_request:
+    branches: [ master ]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# A workflow run is made up of one or more jobs that can run sequentially or in
+# parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the
+    # job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can
+      # access it
+      - uses: actions/checkout@v2
+      - name: Run shellcheck
+        run: shellcheck program.sh