Overhaul and modernise lint and format processes

[Brad-Turner]

• Add prettier, husky and lint-staged
• Modify eslint config
• Remove pretest and precommit package.json scripts, replacing these with husky and lint-staged pre-commit git hooks.
• Rename .eslintrc to .eslintrc.json to future proof ESM compatibility.
• Run npm audit fix to address 2 moderate and 2 critical vulnerabilities.