Dead link in 4.0.1

[oC-n]

Under the Markdown heading, there is a link to a file that doesn't currently exist, showing the notebook in HTML form: [web](https://github.com/alan-turing-institute/rse-course/blob/main/module04_version_control_with_git/04_00_introduction.html)

[jemrobinson]

Do you want to make a PR to fix this @oC-n ? Should be a nice quick one :)

[oC-n]

Can do, @jemrobinson . Was just waiting until I'm sure I've got the procedure right. I'll link to https://github.com/alan-turing-institute/rse-course/blob/gh-pages/html/module04_version_control_with_git/04_00_introduction.html

[jemrobinson]

It might be better to link to https://alan-turing-institute.github.io/rse-course/html/module04_version_control_with_git/04_00_introduction.html which shows the processed HTML.

[oC-n]

Pull request created: #199