chore(docker): improve-docs

[p-fernandez]

What change does this PR introduce?

Adds the environment variable needed for deploying the Web app with Docker in the local environment.

Why was this change needed?

We are having a lot of questions open regarding the Docker setup and not being able to deploy it in the local with fully functional as they receive a CORS error due a wrongly set up environment variable.

Other information (Screenshots)

[gitpod-io[bot]]

[scopsy]

Perfect!