[racket] Scribble HTML preview tool

Maybe there was already a way to do this, but I didn't come across it. I like to be able to preview my Scribble HTML as I'm working on the source. So I built this capability into my Pollen package:

raco pkg install pollen
cd /path/to/scribble/sources
raco pollen start

Then, when you visit http://localhost:8080/index.ptree in your web browser, you'll see a list of your Scribble sources and can click on them to preview. As you edit the source, you can reload the browser and it will update the HTML.

One limitation: this tool only provides single-page previews, and certain formatting will change (e.g., titles) when the source is rendered in multi-page mode.