refactor: Use named exports instead of default exports (#2238)

* use named exports instead of default exports

* fix tests

Co-authored-by: Philipp Kühn <philippkuehn@MacBook-Pro-von-Philipp.local>

packages/html/src/getHTMLFromFragment.ts

@@ -1,7 +1,7 @@
 import { Node, DOMSerializer, Schema } from 'prosemirror-model'
 import { createHTMLDocument, VHTMLDocument } from 'zeed-dom'
 
-export default function getHTMLFromFragment(doc: Node, schema: Schema): string {
+export function getHTMLFromFragment(doc: Node, schema: Schema): string {
   const document = DOMSerializer
     .fromSchema(schema)
     .serializeFragment(doc.content, {