Episode 4 - Version Control: Clarify prerequisites & VSCode usage

[smangham]

Currently, the prerequisites are:

have foundational knowledge of Python, version control and using software tools from command line shell

However, the Git section introduces version control in a way that's too basic for anyone who actually comes in with VC experience, but too fast for anyone who does not. It's also unclear whether it should be done in VSCode or in the command line. The material mentions VSCode briefly, but all the content mentions command-line instructions. You can try and demo the command line and then VS Code, but it involves a lot of back and forth and is not especially clear. The exercises then focus on commit size & commit message practise without reference to the actual code we've got, and use diffs that are hard to read as they're huge images. Then there's also a small bit on reset/revert e.t.c. which people found useful when told, but we don't try.

If the goal is a refresher on Git and an introduction to Git in VS Code and VS Code itself, then it'd be better to do entirely in VS Code.
Commit size/commit message could be done as an exercise on the existing code where we point out a set of flaws (filenames, filenames in the Python file, import statements, something else) and ask them to come up with the commit messages for the fixes, then discuss how "Renamed files"/"Fixed filenames in script"/"Fixed imports" is better than "Fixed everything".
This would also make the section much faster.