feat(nextjs) Update quickstart and manual setup (#15757)

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## DESCRIBE YOUR PR
* Updates quickstart to add a checklist to verify setup
* Manual setup becomes more action driven with each step in the
configuration / feature onboarding having it's own verification step

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---------

Co-authored-by: getsantry[bot] <66042841+getsantry[bot]@users.noreply.github.com>
Co-authored-by: Alex Krawiec <alex.krawiec@sentry.io>

Author: 3 people

docs/platforms/javascript/guides/nextjs/configuration/build/index.mdx

@@ -16,7 +16,7 @@ keywords:
   ]
 ---
 
-The Sentry Next.js SDK supports automatic code injection and source map upload during your app's build process using the `withSentryConfig` wrapper in your Next.js configuration file (`next.config.js` or `next.config.mjs`). For information on updating the configuration, see [Extend Next.js Configuration](../../manual-setup/#extend-your-nextjs-configuration).
+The Sentry Next.js SDK supports automatic code injection and source map upload during your app's build process using the `withSentryConfig` wrapper in your Next.js configuration file (`next.config.js` or `next.config.mjs`). For information on updating the configuration, see the [Manual Setup guide](/platforms/javascript/guides/nextjs/manual-setup/#configure).
 
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