docs(tanstackstart-react): Add source maps quickstart instructions

[nicohrubec]

DESCRIBE YOUR PR

Pointing users to the correct source map setup instructions for the Tanstack Start React SDK.

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[vercel]

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Project	Deployment	Preview	Comments	Updated (UTC)
sentry-docs	Ready	Preview	Comment	Dec 4, 2025 9:34am

1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
develop-docs	Ignored	Preview		Dec 4, 2025 9:34am

[codecov]

Bundle Report

Changes will increase total bundle size by 570 bytes (0.0%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
sentry-docs-server-cjs	24.32MB	576 bytes (0.0%) ⬆️
sentry-docs-client-array-push	10.22MB	-6 bytes (-0.0%) ⬇️

Affected Assets, Files, and Routes:

view changes for bundle: sentry-docs-client-array-push

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
static/chunks/pages/_app-*.js	-3 bytes	893.1kB	-0.0%
static/chunks/9366-*.js	-3 bytes	436.99kB	-0.0%
static/Vj3seEdTVk5z9TsGq5ohY/_buildManifest.js (New)	684 bytes	684 bytes	100.0% 🚀
static/Vj3seEdTVk5z9TsGq5ohY/_ssgManifest.js (New)	77 bytes	77 bytes	100.0% 🚀
static/1sAGGw1ASUJMLgsBrwyOg/_buildManifest.js (Deleted)	-684 bytes	0 bytes	-100.0% 🗑️
static/1sAGGw1ASUJMLgsBrwyOg/_ssgManifest.js (Deleted)	-77 bytes	0 bytes	-100.0% 🗑️

view changes for bundle: sentry-docs-server-cjs

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
1729.js	-3 bytes	5.46MB	-0.0%
6529.js	-3 bytes	4.88MB	-0.0%
../instrumentation.js	-3 bytes	4.78MB	-0.0%
../app/[[...path]]/page.js.nft.json	195 bytes	941.73kB	0.02%
../app/platform-redirect/page.js.nft.json	195 bytes	941.65kB	0.02%
../app/sitemap.xml/route.js.nft.json	195 bytes	939.17kB	0.02%

[inventarSarah]

Thank you for noticing that this was missing and adding it! 🌟