ci: setup pnpm in npm publish workflow (#1176)

Author: hleepfl

.github/workflows/publish-deploy.yml

@@ -18,6 +18,7 @@ jobs:
           registry-url: "https://registry.npmjs.org"
           package-manager-cache: false # never use caching in release builds
           scope: "@epfml"
+      - uses: pnpm/action-setup@v6
       - run: pnpm ci
       - run: pnpm -F 'discojs*' version prerelease --preid=p`date +%Y%m%d%H%M%S`
         if: github.ref_type == 'branch'