Add pagination to the cards endpoint

[filipefigcorreia]

Adds documentation for the newly introduced cards pagination.

[fixe]

@filipefigcorreia please improve the commit title and add a description.

[tfmf]

@filipefigcorreia can you also indicate the number of cards returned per request?

[filipefigcorreia]

@tfmf the number of items will be the one specified in the request through the Range header. Is this what you meant?

[tfmf]

@filipefigcorreia yes, that works.