Replace Docusaurus site with static HTML

docs/docs.js

@@ -0,0 +1,15 @@
+async function loadDoc() {
+  const hash = decodeURIComponent(location.hash.slice(1)) || '01-get-started/01-What-is-Stardust';
+  const file = hash + '.md';
+  const res = await fetch(file);
+  const container = document.getElementById('content');
+  if (!res.ok) {
+    container.textContent = 'Document not found.';
+    return;
+  }
+  let text = await res.text();
+  text = text.replace(/^---[\s\S]*?---\n/, '');
+  container.innerHTML = marked.parse(text);
+}
+window.addEventListener('hashchange', loadDoc);
+window.addEventListener('load', loadDoc);