Pin action version

Author: mhucka

.github/workflows/ci.yaml

@@ -125,7 +125,7 @@ jobs:
         run: echo '::add-matcher::.github/problem-matchers/shellcheck.json'
 
       - name: Run ShellCheck
-        uses: ludeeus/action-shellcheck@master
+        uses: ludeeus/action-shellcheck@00cae500b08a931fb5698e11e79bfbd38e612a38
         with:
           severity: error
           check_together: 'yes'