Add a GH action to deploy a test instance on PRs

.github/workflows/firebase-hosting-pull-request.yml

@@ -0,0 +1,24 @@
+# This file was auto-generated by the Firebase CLI
+# https://github.com/firebase/firebase-tools
+
+name: Deploy to Firebase Hosting on PR
+'on': pull_request
+jobs:
+  build_and_preview:
+    if: '${{ github.event.pull_request.head.repo.full_name == github.repository }}'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+      - name: Run hugo
+        uses: peaceiris/actions-hugo@v2
+        with:
+          hugo-version: 'latest'
+        run: hugo
+      - name: Deploy
+        uses: FirebaseExtended/action-hosting-deploy@v0
+        with:
+          repoToken: '${{ secrets.GITHUB_TOKEN }}'
+          firebaseServiceAccount: '${{ secrets.FIREBASE_SERVICE_ACCOUNT_BENTSUKUN_CH }}'
+          projectId: bentsukun-ch