fix(bautajs-express-example, bautajs-fastify-example): add service to showcase request cancellation

[Xavier-Redondo]

PR Checklist

• I have added/updated documentation for any new behavior.

PR Description

This does not solve anything by itself but it is a previous/helpful step to try to solve the issue #65.

Basically we have added a new endpoint to both fastify and express example services:

• service GET api/cancel/{number}
  • if number is less than 10: the endpoint waits that number of seconds and returns a string.
  • if number is greater than 10: the endpoint will wait 10 seconds and will cancel the request at that moment.

This showcases request cancellations inside bauta pipelines and provides a playground for issue #65.

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[franher]

LGTM