fix: Paragraphs in table cells skipped in import

Port HTML importer rules from enterprise fork

server/utils/turndown/emptyParagraph.ts

@@ -0,0 +1,21 @@
+import TurndownService from "turndown";
+
+/**
+ * A turndown plugin for converting paragraphs with only breaks to newlines.
+ *
+ * @param turndownService The TurndownService instance.
+ */
+export default function emptyParagraphs(turndownService: TurndownService) {
+  turndownService.addRule("emptyParagraphs", {
+    filter(node) {
+      return (
+        node.nodeName === "P" &&
+        node.children.length === 1 &&
+        node.children[0].nodeName === "BR"
+      );
+    },
+    replacement() {
+      return "\n\n\\\n";
+    },
+  });
+}