Update Compound Timeline microsite

[jpveooys]

Description

The documentation on the Compound Timeline microsite needs updating for v3.

This incudes:

• updating information about render props
• updating the TimelineContext example
• updating the Custom Component Presentation example
• removing TimelineSide
• updating the signature of useTimelinePosition to indicate endDate is optional
• updating the Storybook link
• updating package names in installation instructions and code samples
• updating the changelog link
• updating Royal Navy reference in footer

This is not a comprehensive list; there may be other things that need updating.

[jpveooys]

Updates have been made to the staging environment for the content changes (except for the TimelineContext example).

Some code changes are also required, I've made a start on this branch:

https://github.com/defencedigital/design-system-docs/compare/feature/timeline-v3?expand=1

(Unfortunately, it seems Storybook is broken at the moment – I've tried to fix it but there still remains some problem related to icons/SVGR. It may be easier to downgrade that loader than try to update to Webpack 5 as I was.)