feat: add static site generation and GitHub Pages deployment

[zeke]

This PR converts the dynamic Express.js thesaurus application into a static site that can be deployed to GitHub Pages for free, eliminating server hosting costs.

Changes

• Add build script using Puppeteer to scrape all thesaurus pages into static HTML
• Set up GitHub Actions workflow for automated deployment
• Add support for 25,000+ word pages with proper URL routing
• Maintain all existing functionality while enabling static hosting

Testing locally

gh repo clone words/moby
cd moby
gh pr checkout feat/static-site-generation
npm install
npm run build  # Generates static site in ./dist

Prompts

this is a dynamic web server that costs too much money to run. let's convert it into a static website by adding a build step that scrapes the whole site into a directory. publish that directory using github pages and a github actions workflow.

remove the doc about the change. run the build script. gitignore the build script. create a branch. push it. create a pr. open it.