qmk docs: restore --port and --browser arguments

[fauxpark]

Description

These were removed during the move to Vitepress, however vitepress dev does have equivalent arguments.

Documentation for qmk generate-docs has been tweaked to emphasise it's only for emitting the production docs.

I've also adjusted run_docs_command() to make the dev server interactive, which provides a cleaner way to shut down than hitting Ctrl+C.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).