Specify permissions for all workflows

[dhirschfeld]

• https://github.blog/changelog/2021-04-20-github-actions-control-permissions-for-github_token/
• https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token
• https://dev.to/github/the-githubtoken-in-github-actions-how-it-works-change-permissions-customizations-3cgp