Confusing information regarding .env and .lagoon.env based env files

[shreddedbacon]

The following section in the documentation references adding .env and .lagoon.env files into the git repo, but neglects to inform the user that they also need to be added to the Dockerfile, as this is roughly mentioned at the top of the page.

https://docs.lagoon.sh/concepts-advanced/environment-variables/#environment-files-existing-directly-in-the-git-repo

It might be worth including a note in the sub section that the files need to be included in the built images, or structured a bit differently to make it clearer in both areas that the files need to be added to the containers via the Dockerfile for each service that they need to be available in.