Render the playground's integrated browser conditionally on port listening

[ericlery]

What problem are you trying to solve?

Currently, when only doing scripting work that don't involve an HTTP server, the browser on the Deno Deploy Playground is still rendered at the right of the page.

It also displays:

502 Bad Gateway
The deployment failed while serving the request.
Code: ISOLATE_INTERNAL_FAILURE

The console view is too small at the very bottom.

Describe the solution you'd like

Let the console view take the right side of the page when the script doesn't initialize a server.

It could also enable better visibility of the output for hypothetical deployments of isolated Deno Cron jobs, or Deno KV migration scripts: #565

Describe alternatives you've considered

1. Being able to drag, resize, or detach the panels would also be great
2. Tabs like JS Bin that will allow hiding the HTML output when not needed:

[pihentagy]

The Logs pane should be resizable. That also bothers me.