Add official Github action for openapi-diff

Openapi-diff is well suited to be integrate into Github actions in order to:

• Highlight breaking in a pull request
• Document changes in OpenAPI
• etc.

For example, today we have an internal github repo which on every commit triggers generating Redoc OpenAPI documentation and publishes it to Github pages for the repository. In this documentation we'd like to include a openapi-diff markdown report of the changes.

Or, when ever we do a pull request we want to review the changes made. Openapi-diff will allow us to identify automatically breaking changes.

There are a couple of unofficial limited Github actions based on other openapi diff tool

• https://github.com/marketplace/actions/openapi-review
• https://github.com/marketplace/actions/openapi-diff

Comienza revisando los puntos de entrada existentes del repositorio y la configuración de release o automatización; el issue no menciona archivos ni tests. Compara el comportamiento solicitado con las actions no oficiales enlazadas y determina cómo debería exponer una action oficial los resultados de OpenAPI diff y las comprobaciones de breaking changes. Se considera completado cuando una GitHub Action utilizable está documentada y validada para workflows de pull request y generación de informes.