[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/postcss.config.js

@@ -0,0 +1,8 @@
+// If you want to use other PostCSS plugins, see the following:
+// https://tailwindcss.com/docs/using-with-preprocessors
+module.exports = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+}