chore: Lint pinned SHAs in CI

Signed-off-by: ysknsid25 <kengo071225@gmail.com>

Author: ysknsid25

.github/workflows/pinact.yml

@@ -0,0 +1,20 @@
+name: pinact
+
+on:
+  pull_request: { branches: [main], paths: [".github/**"] }
+
+permissions:
+  contents: read
+
+jobs:
+  pinact:
+    name: Check GitHub Actions are pinned to SHA
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with: { persist-credentials: false }
+      - uses: suzuki-shunsuke/pinact-action@896d595f299e71d65b9d28349d6956abe144390a # v3.0.0
+        with: { skip_push: "true", fix: "false" }
+        env:
+          GITHUB_TOKEN: ${{ github.token }}