Introduce automation to keep `pnpm/action-setup` up-to-date

Hello! This issue was created semi-automatically because this repo popped up in a search. Per https://infra.apache.org/github-actions-policy.html, 3rd-party actions such as `pnpm/action-setup` must be referred to by hash and kept up-to-date by automation such as dependabot. It looks like this repo does not pollow this policy yet.

We plan to start enforcing this policy for `pnpm/action-setup` through https://github.com/apache/infrastructure-actions/pull/1193 .

If this was a false posivite, you can close this issue. Otherwise, you likely want to update your workflows, since they will stop working once that PR is merged.

Inizia ispezionando i file dei workflow di GitHub Actions del repository e qualsiasi configurazione Dependabot esistente. Controlla come viene attualmente referenziato `pnpm/action-setup`, quindi confronta la configurazione con la Apache GitHub Actions policy; il lavoro è completato quando l'action è bloccata a una versione specifica ed è coperta da un'automazione che la mantiene aggiornata.

Scritto dal modello di indicizzazione a partire dal testo della issue.