Add artifact attestations

.github/workflows/release.yml

@@ -9,7 +9,9 @@ jobs:
   build:
     runs-on: ubuntu-latest
     permissions:
+      attestations: write
       contents: write
+      id-token: write
     steps:
       - uses: actions/checkout@v3
 
@@ -23,6 +25,13 @@ jobs:
           npm install
           npm run build
 
+      - name: Attest release artifacts
+        uses: actions/attest-build-provenance@v2
+        with:
+          subject-path: |
+            main.js
+            styles.css
+
       - name: Create release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}