fix: Add newline to md formula export (#142)

Add newline to md formula export

Signed-off-by: Rafael Teixeira de Lima <[email protected]>

Author: rateixei

docling_core/types/doc/document.py

@@ -2169,7 +2169,7 @@ def export_to_markdown(  # noqa: C901
 
             elif isinstance(item, TextItem) and item.label in [DocItemLabel.FORMULA]:
                 in_list = False
-                mdtexts.append(f"$${item.text}$$")
+                mdtexts.append(f"$${item.text}$$\n")
 
             elif isinstance(item, TextItem) and item.label in labels:
                 in_list = False