Actions updates

.github/workflows/clang-format-check.yml

@@ -1,9 +1,10 @@
 name: clang-format Check
-on: [push, pull_request]
+on: [workflow_dispatch, push, pull_request]
 jobs:
   formatting-check:
     name: Formatting Check
     runs-on: ubuntu-latest
+    if: "!contains(github.event.head_commit.message, 'skip-ci')"
     steps:
     - uses: actions/checkout@v2
     - name: Run clang-format style check for C programs.