Add attachments docs for Node SDK

[AbhiPrasad]

Core or SDK?

Platform/SDK

Which part? Which one?

@sentry/node

Description

Attachments support has been added for the Node SDK, but the docs for attachments only show up on the browser SDK: https://docs.sentry.io/platforms/javascript/enriching-events/attachments/.

Suggested Solution

Make sure that the Node SDK docs have details about how to use attachments under the Enriching Events title