Add health check endpoints

[rragundez]

At the moment the documentation does mention health check endpoints but I think they are a standard in applications and they should be included already as part of the source code. Would be helpful to users to just have them.

This PRs adds the functionality to enable the checking of the services and created 2 health check endpoints. The first one just on the app itself /health which normally would be used for autoscaling rules and such and a /ready endpoints which would normally will be used by load balancers to start directing traffic. Other uses are also possible.
The PR also updated the documentation in the relevants parts to take into account the addition of the endpoints in the source code.

As a general remark, I think this repository is very well done in terms of functionality, design, and code quality, therefore I think it should be more opinionated and some of the things in the docs should not be a suggestion but actually help the user by having them already as best practices, for example: middleware for CORS and Security headers and maybe the api-key per user functionality.

[LucasQR]

This looks great, thanks the contributions