Add mobile-tables.html fetched from simonw.github.io/private-hosted (#239)

> Fetch https://gist.githubusercontent.com/simonw/28893229c07d9f5cc80fbd185ca61a87/raw/c471e60a50712dc29fbb9635829e8b4aaac86827/mobile-tables.md to /tmp using curl and then read it and create a single demo page (no React) that illustrates ALL of the ideas in that document. Call it mobile-tables.html

> Run “uvx rodney –help” and then use rodney to help test it

Author: simonw