fix(nextjs): Add next as a peer dependency

[lobsterkatie]

Since there are now a few different places in our code where we import things from next, it should be a dependency. That said, anyone using the SDK presumably already has next installed, so this PR makes it a peer dependency rather than a regular dependency.

Fixes #3490.

[github-actions]

size-limit report

Path	Size
@sentry/browser - CDN Bundle (gzipped)	20.63 KB (+0.01% 🔺)
@sentry/browser - Webpack	21.5 KB (0%)
@sentry/react - Webpack	21.53 KB (0%)
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	27.92 KB (+0.01% 🔺)

[HazAT]

Want to add that we need next 10.0.8 because they fixed a bug there which our SDK relies on.
I don't have a link to the issue but a customer reported it.

[lobsterkatie]

Want to add that we need next 10.0.8 because they fixed a bug there which our SDK relies on.
I don't have a link to the issue but a customer reported it.

They reported it through one of our sales engineers, I believe, who passed the feedback onto us in slack:

I've started experimenting with the NextJS integration.

I noticed on https://docs.sentry.io/platforms/javascript/guides/nextjs/, it states:

Currently, the minimum Next.js supported version is 10.0.0.

Our app is currently using 10.0.3, but I was running into an issue when I added withSentryConfig to my next.config.js file. From what I could tell, the issue was due to this instrumentServer call:

sentry-javascript/packages/nextjs/src/index.server.ts

Line 34 in 4bbb553

instrumentServer();

Which in turn creates a nextServer:

sentry-javascript/packages/nextjs/src/utils/instrumentServer.ts

Line 42 in 4bbb553

const nextServerPrototype = Object.getPrototypeOf(createNextServer({}));

Which tries to load the next.config.js file and results in this:

`warn  - Detected next.config.js, no exported configuration found. https://err.sh/vercel/next.js/empty-configuration`

I noticed that there were some config loading changes in 10.0.8, namely: vercel/next.js#22578 and so I tried upgrading and that seemed to resolve the issue.

Wanted to give you the heads up so your team can confirm and update that note in the docs about the minimum required version of NextJS.

The issue is that before 10.0.8, config loading was sync rather than async.

H/t to the original reporter!