📝 Clarify how to run locally

[CollierCZ]

Motivation and Context

It wasn't clear immediately what the PORT variable was and how to run the server.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation

Checklist:

Go over all the following list, and put an x in all the boxes that apply. If you're unsure about what any of these mean, don't hesitate to ask. We're here to help!

• I have read the contribution guide
• I have created an issue following the issue guide
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[OriPekelman]

By convention "local development http ports" should default to 8080 or 8000 otherwise it may seem like there is a special magical meaning to the port number, which isn't the case here, any port would do. Considering this is Python and python -m http.server uses 8000 as its default I would suggest that port number.

[CollierCZ]

I updated the port and added a note about it being possible to use any port.