Add sign-package job to ci.yml

Signed-off-by: Tsuyoshi Hombashi <tsuyoshi.hombashi@gmail.com>

.github/workflows/ci.yml

@@ -76,6 +76,34 @@ jobs:
           repository-url: https://test.pypi.org/legacy/
           skip-existing: true
 
+  sign-package:
+    needs: build-package
+    runs-on: ubuntu-latest
+    concurrency:
+      group: ${{ github.event_name }}-${{ github.workflow }}-${{ github.ref_name }}-sign-pkg
+      cancel-in-progress: true
+    timeout-minutes: 20
+    permissions:
+      id-token: write
+
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: dist
+          path: ./dist
+
+      - name: Sign the dists with Sigstore
+        uses: sigstore/gh-action-sigstore-python@v2.1.1
+        with:
+          inputs: >-
+            ./dist/*.tar.gz
+            ./dist/*.whl
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: sigstore
+          path: ./dist/*.sigstore
+
   lint:
     runs-on: ubuntu-latest
     concurrency: