Images should be converted to webp (and other improvements)

[MTecknology]

All images should be:

• [x] Converted to webp format - example
• [x] Added to preload - example

We should also:

• [ ] Add a very basic/lightweight background
• [x] Add a subheading to demo site configurations (with improved CSS)
• [x] Lighten clouds image slightly (avoid eye strain)
• [x] Change "clouds.png" to "banner.*"
• [x] Increase contrast on copyright/source (consider colorblind users)
• [x] Add alt="logo" width=? height=? to layouts/partials/logo.html
• [x] Add rel="preconnect" to<style $googleFontsLink in layouts/_default/baseof.html
• [x] Tack on a synchronization with mainroad
• [x] Add meta description (from site description)