Add github actions shellcheck workflow

.github/workflows/shellcheck.yml

@@ -0,0 +1,9 @@
+name: lint
+
+on: [push, pull_request]
+
+jobs:
+  shellcheck:
+    - runs-on: ubuntu-latest
+    - name: shellcheck
+      uses: ludeeus/action-shellcheck@0.1.0