[examples/data-literate][m]: factor our a working markdown+CSV (data literate) example from site (where we already had a demo).

* removed a few extraneous things
* added the README.md with some instructions

examples/data-literate/pages/[...slug].js

@@ -0,0 +1,48 @@
+import fs from 'fs'
+import path from 'path'
+
+import parse from '../lib/markdown.js'
+
+import DataLiterate from '../components/DataLiterate'
+
+import { postFilePaths, POSTS_PATH } from '../lib/mdxUtils'
+
+
+export default function PostPage({ source, frontMatter }) {
+  return (
+    <DataLiterate source={source} frontMatter={frontMatter} />
+  )
+}
+
+export const getStaticProps = async ({ params }) => {
+  const mdxPath = path.join(POSTS_PATH, `${params.slug.join('/')}.mdx`)
+  const postFilePath = fs.existsSync(mdxPath) ? mdxPath : mdxPath.slice(0, -1)
+  const source = fs.readFileSync(postFilePath)
+
+  const { mdxSource, frontMatter } = await parse(source)
+
+  return {
+    props: {
+      source: mdxSource,
+      frontMatter: frontMatter,
+    },
+  }
+}
+
+export const getStaticPaths = async () => {
+  var paths = postFilePaths
+    // Remove file extensions for page paths
+    .map((path) => path.replace(/\.mdx?$/, ''))
+
+  // Map the path into the static paths object required by Next.js
+  paths = paths.map((slug) => {
+    // /demo => [demo]
+    const parts = slug.slice(1).split('/')
+    return { params: { slug: parts } }
+  })
+
+  return {
+    paths,
+    fallback: false,
+  }
+}