Docs for customizing starting a dev server

[jwoertink]

This section should mention show to use the DEV_PORT env and also how the config/watch.yml works.
https://luckyframework.org/guides/getting-started/starting-project#start-the-server

To change your port or host, you update your config/watch.yml, but if you use overmind or other such process runners, these use PORT which causes your config/watch.yml to be ignored, so you need to use DEV_PORT or DEV_HOST env. However, because the .env file isn't read until runtime, you need the DEV_PORT and DEV_HOST values to exist before compile time which means they need to be specified in the CLI (e.g. DEV_PORT=3004 lucky dev)