feat: Add HTML export option (#4056)

* tidy

* Add title to HTML export

* fix: Add compatability for documents without collab state

* Add HTML download option to UI

* docs

* fix nodes that required document to render

* Refactor to allow for styling of HTML export

* div>article for easier programatic content extraction

app/utils/download.ts

@@ -67,7 +67,6 @@ export default function download(
     if ("download" in a) {
       a.href = url;
       a.setAttribute("download", fn);
-      a.innerHTML = "downloading…";
       D.body && D.body.appendChild(a);
       setTimeout(function () {
         a.click();