issue atlassian-api#280: adapt documentation

Author: andreas-j-hauser

docs/confluence.rst

@@ -92,6 +92,10 @@ Page actions
     # automatically version the new file and keep the old one
     confluence.attach_file(filename, page_id=None, title=None, space=None, comment=None)
 
+    # Attach (upload) a content to a page, if it exists it will update the
+    # automatically version the new file and keep the old one
+    confluence.attach_content(content, name=None, content_type=None, page_id=None, title=None, space=None, comment=None)
+
     # Export page as PDF
     # api_version needs to be set to 'cloud' when exporting from Confluence Cloud. 
     confluence.export_page(page_id)