fixed some things. and did some UI changes

js/post/download.js

@@ -0,0 +1,18 @@
+document.addEventListener("DOMContentLoaded", () => {
+  // current page URL
+  let url = window.location.href; 
+
+  // replace `/html/` with `/markdown/`
+  url = url.replace("/html/", "/markdown/");
+
+  // replace `.html` with `.md`
+  url = url.replace(/\.html$/, ".md");
+
+  // assign to <a>
+  const a = document.getElementById("download-md");
+  a.href = url;
+
+  // suggest filename
+  const filename = url.split("/").pop(); // e.g. markdowntest.md
+  a.download = filename;
+});