Add details to the optional fork-and-PR challenge

[alex-ball]

This pull request addresses several issues with the optional challenge in Episode 5 to clone someone else's repository locally and use it to initiate a pull request:

1. The heading and introductory paragraph should be inside the challenge fenced div, not before it in a block quote.
2. The introductory paragraph should explain why someone would want to do it (issue Optional GitHub challenge needs expanding #132).
3. Instead of taking learners through the steps directly, it tells them to look at an external set of instructions. But the external instructions aren't there any more (issue Broken link to "Time to Submit Your First PR" #175), and in any case involved forking an entirely different third party repository (which has since been removed).

The replacement text here fixes the formatting, adds some reasons why this workflow might be preferable, and provides a full set of steps that mirror the previous challenge, including screenshots.

I would welcome any improvements that can be made to these new steps.

Closes #132. Closes #175.

[github-actions]

Thank you!

Thank you for your pull request 😃

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Rendered Changes

🔍 Inspect the changes: https://github.com/LibraryCarpentry/lc-git/compare/md-outputs..md-outputs-PR-181

The following changes were observed in the rendered markdown documents:

 05-github-pages.md               | 132 ++++++++++++++++++++++++++++++++++-----
 fig/github-fork-button.png (new) | Bin 0 -> 16809 bytes
 fig/github-fork-clone.png (new)  | Bin 0 -> 57518 bytes
 fig/github-pr-create.png (new)   | Bin 0 -> 27006 bytes
 md5sum.txt                       |   2 +-
 5 files changed, 117 insertions(+), 17 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 2025-07-08 09:12:14 +0000

[alex-ball]

@srerickson , do these changes look good to you?

[srerickson]

Sorry for the delay-- this looks great!