Revision: Overhauled coursework, general themes listed

[SallyMcGrath]

Changes:

• Ordered all coursework in a coherent sequence
• Removed excessively mathy or repetitive assignments
• Constructed each problem as https://cafe.cognitiveload.com.au/kb/fadedworkedexamples
• Scaffolded test script files, import statements, and package.json
• Introduced guidance about using VSCode Test Runner
• All test files have a minimal test
• Annotated writing tasks with clear ======> for trainees to put their answers to make it easier for code reviewers to find them
• Updated the readmes to match all this
• Added many pleas for them to do the prep first