fix: add TableKit to preserve GFM tables on updatePage

Closes #2

GFM tables were corrupted when using update_page because the
Markdown → HTML (marked) → ProseMirror JSON (generateJSON) flow did not
recognize <table>, <tr>, <th>, <td> elements. Adding TableKit from
@tiptap/extension-table registers the required schema so tables round-trip
correctly in both create and update flows.

Tested on Docmost 0.70.1. Fixes PR #6 from the original repo.

src/lib/tiptap-extensions.ts

@@ -1,9 +1,11 @@
 import StarterKit from "@tiptap/starter-kit";
 import Image from "@tiptap/extension-image";
 import Link from "@tiptap/extension-link";
+import { TableKit } from "@tiptap/extension-table";
 
 // Define extensions compatible with standard Markdown features
 // We use the default Tiptap extensions to handle basic content
+// TableKit is required for generateJSON to parse HTML tables from marked (GFM tables)
 export const tiptapExtensions = [
   StarterKit.configure({
     // Explicitly enable features that might be disabled in some contexts
@@ -16,4 +18,5 @@ export const tiptapExtensions = [
   Link.configure({
     openOnClick: false,
   }),
+  TableKit,
 ];