docs: More node docs

[mydea]

Some more node docs for v8, including:

• How to add custom OTEL instrumentation
• How to use with custom OTEL setup
• How to setup non-framework node apps

[Lms24]

General comment: I think it's good that we write down these changes but I'm curious if we're considering moving this doc in some capacity to sentry docs?

[Lms24]

Do we need to adjust this docs page (for v8)?
https://docs.sentry.io/platforms/node/performance/instrumentation/opentelemetry/

[mydea]

we'll need to adjust more or less all the node docs, eventually 😬 so yes!

[mydea]

General comment: I think it's good that we write down these changes but I'm curious if we're considering moving this doc in some capacity to sentry docs?

Definitely! It's a bit of a tricky place because we can't really update them yet because the new stuff is not stable 😬 So I'd keep docs here for now, so we have something to point people to who want to try out the new stuff. And when we come close to being stable (e.g. beta territory), we can start to move these into sentry-docs proper, I'd say?

[Lms24]

Sounds good! When we're ready, we can also open PRs in docs before we go stable with v8 and only merge them afterwards. But it def makes sense to have something to point people to in the meantime. Thanks!