Fix: First time developer setup

[NiceGuyIT]

While setting up the dev environment for the first time, I ran into some issues. This PR fixes .env.example to help future developers.

1. The nginx container uses port 443 which is coming from DEV_PORT in tacticalrmm/.devcontainer/.env. These need to match.
2. Vue was throwing a "DOMException: The operation is insecure" error because it's using ws://. Adding DOCKER_BUILD causes Vue to use wss://, solving the problem.

[wh1te909]

I don't use docker for dev so as long as this still works for @sadnub fine by me

[sadnub]

I think that .env file is actually used in production, so setting the DOCKER_BUILD to false in that file will work.