Docs: Refactor `draftMode()` page to follow template, document missing methods, improve guide (#69616)
Closes:
https://linear.app/vercel/issue/DOC-3297/draftmode-reference-page
- Documents missing methods
([source](https://github.com/vercel/next.js/blob/adc94b49d47cd263140ba6523bc2db2e6d09e0d2/packages/next/src/client/components/draft-mode.ts#L6))
- Adds examples
- Review and improve Draft Mode guide.
Will add the steps component once we start working on the guides.
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Co-authored-by: Rich Haines <hello@richardhaines.dev>