Merge pull request #1158 from Ralim/shellcheck

Adding Shellcheck to CI

.github/workflows/shellcheck.yml

@@ -0,0 +1,15 @@
+name: Shell Check
+on: [pull_request]
+jobs:
+  shellcheck:
+    name: runner / shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: shellcheck
+        uses: reviewdog/action-shellcheck@v1
+        with:
+          github_token: ${{ secrets.github_token }}
+          reporter: github-pr-review # Change reporter.
+          exclude: "./.git/*" # Optional.
+          check_all_files_with_shebangs: "false" # Optional.