docs(recipes): add recipe for Apitally (monitoring)

[itssimon]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Docs
• Other... Please describe:

What is the current behavior?

n/a

What is the new behavior?

The docs now contain a recipe page for setting up Apitally to monitor a NestJS app.

Does this PR introduce a breaking change?

• Yes
• No

Other information

Apitally is a simple API monitoring and analytics tool. It integrates with NestJS via a lightweight middleware and provides:

• Real-time metrics for API usage, errors, and performance
• Consumer-level insights and API adoption tracking
• Request and application logs with automatic correlation
• Uptime monitoring and alerting