Update docs section about using the Action in public forks.
Add warning about current issue when the forks lives under an organisation.
Mark section about running a workflow in the head repository as outdated, as I was not able to reproduce this in test projects.
See https://github.com/stefanzweifel/git-auto-commit-action/issues/211#issuecomment-1428849944 for more details.
Starting February 2nd 2023, GitHub changed the default permissions of the GITHUB_TOKEN to be read-only in all new repositories.[1]
git-auto-commits needs `write`-permissions for the `contents`-key in order to work properly.
This commits updates the usage section, to mention the need for the permission requirements. The examples have also been updated to reflect that change.
[1]: https://github.blog/changelog/2023-02-02-github-actions-updating-the-default-github_token-permissions-to-read-only/
Stefan Zweifel