Describe in more detail how to create links and actions through the available SPI

[ingogriebsch]

Chapter https://spring-hateoas-siren.ingogriebsch.de/1.1.0/index.html#serialization-links needs to be reworked.
It needs to explain how Siren Links and Actions are created based on the available SPI (i.e. Spring HATEOAS Links and Affordances).
Have a look at the Spring HATEOAS documentation and how the HAL-Forms chapter explains the details.