Add documentation for Deckard's fields/methods usage with different use cases

[lucasoares]

This issue proposes the addition documentation for Deckard covering the usage of its fields and methods in different use cases. The documentation will serve as a valuable resource for developers, providing clear instructions and examples on how to use Deckard's features effectively.

Example:

• breakpoint field - commonly used when a message is used to process a large number of elements, enabling the worker applications to track the progress and resume from where it left off. For example, if we have a social media page with 10,000 posts and need to process them in batches of 10, the "breakpoint" field allows the application to store the last processed position, ensuring it can continue from there in subsequent iterations on different workers.

[lucasoares]

We improved the documentation of our message fields: https://github.com/takenet/deckard/blob/main/docs/proto.md