I've put this command line app together to make working with custom html and css locally for itch game (and profile and gamejam) pages a little easier.

https://www.npmjs.com/package/itchpack

It fetches your current content, processes sass to css, adds "custom-" to html classes, handles css vendor prefixing, base64 encodes images and fonts in css, and some other stuff, and it's easy to keep the unprocessed source code in version control.

Here's what the CLI itself looks like in use: https://asciinema.org/a/384341?speed=2&autoplay=1  (live reloading in browser not shown, but it does that too)

It's essentially a wrapper around webpack with one use in mind

Hope it's helpful to somebody :)

[edit] itchpack now supports pug templates, and can generate your HTML content from a json or yaml data file