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

server/validation.ts

@@ -25,7 +25,7 @@ export function assertArray(
 
 export const assertIn = (
   value: string,
-  options: (string | undefined | null)[],
+  options: Primitive[],
   message?: string
 ) => {
   if (!options.includes(value)) {