add shell check gh action

.github/workflows/blank.yml

@@ -0,0 +1,18 @@
+# from here: https://github.com/marketplace/actions/shellcheck
+- name: ShellCheck
+  # You may pin to the exact commit or the version.
+  # uses: ludeeus/action-shellcheck@d586102c117f97e63d7e3b56629d269efc9a7c60
+  uses: ludeeus/action-shellcheck@1.0.0
+#  with:
+#    # A space seperated list of additional filename to check
+#    additional_files: # optional, default is 
+#    # Paths to ignore when running ShellCheck
+#    ignore: # optional, default is 
+#    # Minimum severity of errors to consider. Options: [error, warning, info, style]
+#    severity: # optional, default is 
+#    # Run shellcheck on _all_ files at once, instead of one at a time
+#    check_together: # optional, default is 
+#    # Directory to be searched for files. Defaults to .
+#    scandir: # optional, default is .
+#    # Set to true to skip using problem-matcher
+#    disable_matcher: # optional, default is false