* [site,seo][xs]: add custom _document with lang prop, add description to meta tags, make title larger
* [site,seo][xs]: add apple touch icon, add alt props to images
* [site,seo][xs]: add icon to default seo
* [site,seo][s]: implement next-sitemap
* [site,seo][s]: review page titles
* Rebuild package-lock.json files
* Regenerate package-lock
* Nav bar and layout
* Main catch all route that loads material from content
* Data Literate: demo plus all associated components
* content/data-literate/demo.mdx
* components/* (pretty much all are related to demo)
* lib/markdown.js, lib/mdxUtils.js
* api/proxy.js to proxy remote urls (to handle CORs)
* content/data-literate.md (DL home page - old data literate home page converted to markdown)
* excel-viewer.js: excel viewer demo from data literate
* package.json / yarn.lock
* Nav: @headlessui/react @heroicons/react/outline @heroicons/react
* CSV support for table: papaparse
* Excel support for tables etc: xlsx
* Vega: react-vega vega vega-lite
* MDX: next-mdx-remote (yarn rm @next/mdx)
