Improve introduction of pull requests

[tobyhodges]

How could the content be improved?

We introduce the concept of branches just before the pull request demo+exercise, and I still find it difficult to do this elegantly and efficiently, e.g. judging the right level of detail to provide that will make sense without getting stuck in the weeds of a topic that can be conceptually rather heavy. I would like to expand/polish up the introductory paragraph.

One analogy I have used successfully is to the "Suggestion mode" of GoogleDocs, describing the PR workflow as similar to suggesting edits to somebody else's document: it is more polite, easier to keep track of what changes are being made and by whom, and provides a quality control step.

I also think this is a part of the curriculum that could really benefit from an illustration to share during training.

Which part of the content does your suggestion apply to?

https://carpentries.github.io/lesson-development-training/collaborating-team.html#managing-contributions