Add formatting check workflow for PRs

.github/workflows/clang-format

@@ -0,0 +1,30 @@
+name: Check formatting
+
+on: pull_request
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  format-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: reviewdog/action-setup@v1
+
+      - name: Check formatting on changed lines
+        env:
+          REVIEWDOG_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          git clang-format --diff origin/${{ github.base_ref }}...HEAD -- \
+            '*.c' '*.cpp' '*.cc' '*.h' '*.hpp' \
+            | reviewdog \
+                -name="clang-format" \
+                -f=diff \
+                -reporter=github-pr-review \
+                -fail-level=error \
+                -filter-mode=added