feat: split to components

[jim-at-stink]

Splitting the single big chunk of example and test code in App.tsx into a set of components in components and state.

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[jim-at-stink]

@adrian-at-stink I've changed the react component definitions to use the function keyword now instead of arrow functions. Component file names are CamelCase.

Tried useMemo as suggested but it didn't play nice with the replay visualizer factory, so left as useEffect for now. Will review all that again later if that's ok.

Can you take another look, and submit a review, when you get a mo'.

EDIT: Hold that thought. Lint error I'd missed. Will fix that first. Back on again, please do check now, it was an out of date test that was showing the error. Thanks!

[adrian-at-stink]

@jim-at-stink - looks good to me