Extend API project Github Actions for CI/CD for Staging and Prod slots

[pkskelly]

Enable deployment slots for API to allow for a staging environment.

Review the CI/CD jobs and deployment steps in the link below.
https://github.com/fullstackmaddy/web-api-cicd-githubactions/blob/main/src/Poke.API.Facade.UnitTests/HttpClientTests/PokeApiHttpClientTests.cs