Check coding style with GitHub CI

Close #6

.github/workflows/format.yml

@@ -0,0 +1,17 @@
+name: Format CI
+
+on: [push, pull_request]
+
+jobs:
+  check-format:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repository
+        uses: actions/checkout@v3
+      - name: Check code format
+        run: |
+          FILES=$(find | grep -E "\.(c|h)\$")
+          for file in ${FILES};
+          do
+              clang-format -n -Werror ${file}
+          done