Update docs for fine-grained GitHub tokens

Description

Following my exchange with @travi on GitHub's "Fine-grained personal access tokens" discussion, here's an issue to keep track of the notes I took, changes to be made, and to ask/receive feedback. Please let me know if I forgot anything!

Important points

• When using GitHub Actions, this is only necessary when using branch protection, otherwise, using the permissions feature in workflows as described in the GitHub Actions documentation is enough.
• When pushing to GitHub from other CI tools, using fine-grained PAT will increase the security in contrast to using a regular PAT (regardless of branch protection settings).
• Make clear that using a PAT is only needed to bypass branch protection, which is not relevant when not using @semantic-release/git (https://github.com/semantic-release/git/issues/477)

Documentations to be updated

• usage/ci-configuration#authentication

  • update the GH_TOKEN variable descriptions
  • add a section specifically for GitHub PAT (regular vs fine-grained) explaining the functioning and the security enhancements over regular PAT

• recipes/ci-configurations/github-actions#pushing-package.json-changes-to-a-master-branch

  • update the note about using a PAT to circumvent branch protection settings
  • add a link to the newly added "GitHub PAT" section

• semantic-release/git README > Git authentication

  • add a link to the newly added "GitHub PAT" section
  • add required fine-grained scopes for the plugin

• semantic-release/github README > GitHub authentication

  • add a link to the newly added "GitHub PAT" section
  • add required fine-grained scopes for the plugin

Resources

• StackOverflow - "Github: Pushing to protected branches with fine-grained token"

Feedback wanted

• should we create the "GitHub PAT" section outside the CI configurations dropdown? if so, where do you think would be the most appropriate?

Start with the authentication sections in usage/ci-configuration and the linked semantic-release/git and semantic-release/github README sections. Update the GH_TOKEN descriptions, document regular versus fine-grained PATs and required scopes, and revise the branch-protection notes with cross-links. Done means all listed documentation locations consistently reflect the requested guidance.