refactor to leverage default `prerender` instead of puppetter

[thescientist13]

Type of Change

• New Feature Request
• Improvement / Suggestion
• Bug
• Other (please clarify below)

Summary

With the introduction of Greenwood with WCC and moving Puppeteer out of core, it might make sense to make plans to move this repo to be a little leaner.

Details

1. Drop PostCSS (CSS in JS)
2. Drop LitElement
3. Might need to vendor Slider