Document the need to setup access token for update-workflows.yaml

[ns-rse]

The update-workflows.yaml needs a personal access token to be generated and added to the repository in order for updates to the up-stream workflows and package cache to run correctly.

The instructions are included when there is no token and are as follows...

⚠️ Missing Token

The SANDPAPER_WORKFLOW secret is missing, invalid, or does not have the right scope (public_repo, workflow) to update the package cache.

If you want to have automated pull request updates to your package cache, you will need to generate a new token.
Steps to Generate a New Token

🔑 Click here to generate a new token called Sandpaper Token (slackline/tmp-test) with the public_repo and workflow scopes from your GitHub Account
📋 Copy your new token to your clipboard
Go To https://github.com/ns-rse/tmp-test/settings/secrets/actions/new
enter SANDPAPER_WORKFLOW for the 'Name'
📥 paste your token for the 'Value'