[DOCS / LINTING ISSUE] Provide clear steps if port 3000 is in use

https://v3.docs.apostrophecms.org/guide/setting-up.html#creating-a-project

Why in the hell did you choose port 3000 for the ApostropheCMS server ?

If you work with Node.js you will know that most web app back ends use port 3000 (http) and 3001 (https) for their user-event servers.

But you just went ahead and created a conflict between the app backend and the app's CMS servers over access to port 3000 . . .

Thanks, Ernie & Bert.

Start with the linked setting-up guide page and review its instructions around the ApostropheCMS server port. Update the documentation to explain what to do when port 3000 is already in use, then verify that the steps clearly address the reported Node.js application conflict.

Written by the indexing model from the issue text.