Do not open a new browser window if one is already open

[JakeSCahill]

What's the problem this feature will solve?

When you run http-server -o multiple times, it always opens a new window. If you're testing changes locally, you can end up with lots of windows open.

Describe the solution you'd like

A CLI option to open an existing open window.

Alternative Solutions

Additional context

[github-actions]

This issue has been inactive for 180 days