Add a static site generator

There is no build for the element or site utilities like PrismJS yet, so this site only works locally at the moment.

docs-src/_data/api.11tydata.js

@@ -0,0 +1,8 @@
+const fs = require('fs');
+
+module.exports = () => {
+  const customElements = JSON.parse(fs.readFileSync('custom-elements.json', 'utf-8'));
+  return {
+    customElements,
+  };
+};