ReadMe: Add use cases and patterns implemented section

[JavierCane]

Add a new top level section to the README.md file with the following contents:

Use cases and patterns implemented

• Hexagonal Architecture layers
• Adapter pattern implemented in any of the repositories
• Rich Domain models (tell don't ask, avoid anemic domain models)
• Sync command bus
• Async command bus
• Queue worker
• Mention the Specification pattern implementation used for the backoffice use case. That is, we would use the VideoRepository#searchByCriteria(Criteria $criteria): Videos; method while searching Videos using different Criteria. Common use case for the backoffice of our applications

Important: We should reference a piece of code illustrating each one of the use cases or patterns. Something very similar to what we've done in the Scala API repo with the Libraries and implementation examples README.md section