update GitHub account setup instructions

[tobyhodges]

If this pull request addresses an open issue on the repository, please add 'Closes #NN' below, where NN is the issue number.

Fixes #145

Please briefly summarise the changes made in the pull request, and the reason(s) for making these changes.

This adds guidance for learners about setting up multi-factor authentication. It outsources most of the configuration instructions to GitHub themselves, as the interface and process may change relatively often.

I also replaced the previous instructions for installing Git with links to the Git section of the Installation Instructions page of the workshop website template, as these are more comprehensive and will be updated if and when the steps change to set up command line Git.

If any relevant discussions have taken place elsewhere, please provide links to these.

This change was discussed with Maintainers of other Git lessons in The Carpentries, and further by the @LibraryCarpentry/curriculum-advisors.

[github-actions]

Thank you!

Thank you for your pull request 😃

🤖 This automated message can help you check the rendered files in your submission for clarity. If you have any questions, please feel free to open an issue in {sandpaper}.

If you have files that automatically render output (e.g. R Markdown), then you should check for the following:

• 🎯 correct output
• 🖼️ correct figures
• ❓ new warnings
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Rendered Changes

🔍 Inspect the changes: https://github.com/LibraryCarpentry/lc-git/compare/md-outputs..md-outputs-PR-152

The following changes were observed in the rendered markdown documents:

 md5sum.txt |  2 +-
 setup.md   | 46 +++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 4 deletions(-)

What does this mean?

If you have source files that require output and figures to be generated (e.g. R Markdown), then it is important to make sure the generated figures and output are reproducible.

This output provides a way for you to inspect the output in a diff-friendly manner so that it's easy to see the changes that occur due to new software versions or randomisation.

⏱️ Updated at 2023-09-25 09:28:42 +0000

[emcaulay]

Thank you, Toby! I appreciate your having written up a clear and thorough guide for someone to get a GitHub account set up appropriately.