Mention Token setting in actions

[amouat]

The docs currently read:

To enable the action to create a pull request (open_pr: true) , you will need to create a new token with the correct scope. This is needed because the default GITHUB_TOKEN doesn't have the necessary permissions (workflows).

But I think there is also an setting under settings -> actions that allows you to explicitly allow actions to create PRs. I'm not sure which method is preferable.