fix(nextjs): Add back browser field in package.json

[lforst]

Fixes#6808

Some build pipelines that run outside of Next.js look at the browser field in the package.json to import package code that is intended for the browser.

With #6753 we removed the browser field, thinking it wasn't necessary, breaking tooling like Storybook which now imported Node code.

This PR adds back the browser field, but we need to add another multiplexer entry point because Next.js will also look at the browser field to import SDK code for the Edge runtime.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.82 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	61.44 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.49 KB (+0.02% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	54.74 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	20.22 KB (0%)
@sentry/browser - Webpack (minified)	66.17 KB (0%)
@sentry/react - Webpack (gzipped + minified)	20.24 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.51 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.73 KB (+0.03% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.01 KB (-0.01% 🔽)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	43.11 KB (-0.83% 🔽)
@sentry/replay - Webpack (gzipped + minified)	38.45 KB (-0.99% 🔽)

[ezhlobo]

@lforst thank you for fixing this, could you please drop a line here when and in what version it's published to npm? 🙏

[lforst]

@ezhlobo The new release is out! https://github.com/getsentry/sentry-javascript/releases/tag/7.31.1 Let me know if it resolves the issue for you!

[ezhlobo]

@lforst yes, it works well now! Thank you very much for a very quick fix and for notifying me.