Set permissions for Github Workflows

Hi, I work on behalf of Google and the OpenSSF to help open source projects to increase their supply chain security by using OpenSSF Scorecard as a guide.

I would like to suggest a PR to set up top level permissions to the github workflows in order to grant any write permissions only on the run level.

This is needed because, by default, github grants write-all permission to all workflows, which could be exploit by an attacker in case of a compromised workflow. Limiting permissions is a simple and effective way to also limit the impact of an eventual compromised workflow.

Thus, it is both a recommendation from OpenSSF Scorecard and the Github to always use credentials that are minimally scoped.

Let me know if the PR is welcome and feel free to reach me out in case of any doubts or concerns.

Locate the repository's GitHub workflow files and review their current permission settings against the OpenSSF Scorecard and GitHub Actions guidance linked in the issue. The work is done when workflows have restrictive top-level permissions and any required write permissions are granted only at the relevant run level.