Improve user guide ahead of the Data Week Our Handbook Workshop

[NatalieZelenka]

• Add more details to instructions for what/how to edit:
• Roles of team facilitator (member of the group who is most familiar with GitHub) and team members, e.g. facilitator will fork the repo and turn on the issues. Members will make issues, clone the repo, etc.
• Detailed instructions on how to collaborate for the team on GitHub, e.g. will team members be forking the fork? Or working on their own development branches that they have cloned from the fork?
• Send ahead of time?

[NatalieZelenka]

• Make sure that the existing user guide makes sense for a workshop that is organised for multiple groups rather than them organising their own, e.g. https://very-good-science.github.io/our-handbook/guide/how-to-use/editing-together.html#preparations

[NatalieZelenka]

Also, @ekuw is merging things from the old handbook user guide repository (here: https://github.com/very-good-science/our-handbook-user-guide/issues) - this will soon be archived.