GitHub Workflows security hardening

[sashashura]

This PR adds explicit permissions section to workflows. This is a security best practice because by default workflows run with extended set of permissions (except from on: pull_request from external forks). By specifying any permission explicitly all others are set to none. By using the principle of least privilege the damage a compromised workflow can do (because of an injection or compromised third party tool or action) is restricted. It is recommended to have most strict permissions on the top level and grant write permissions on job level case by case.

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[sashashura]

@remy could you please review?

[sashashura]

An example of a workflow run with unrestricted permissions:

[remy]

I don't really understand the impact of this change. Specifically, I use actions to complete semantic release based releases and I don't know if this has an impact.

A more practical "this is what the change actually does for you" would be ideal (and appreciated). Assume I have the least knowledge...