Feature to create directly addressed Todos when mentioned in beginning

What does this MR do?

Adds a feature to create a 'directly addressed' Todo when @user (or multiple users) are mentioned in the beginning of a note.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #24976 (closed)

lib/banzai/querying.rb

@@ -42,7 +42,6 @@ def filter_nodes?(reference_options)
       reference_options && reference_options[:location] == :beginning
     end
 
-
     # Selects child nodes if they are present in the beginning among other siblings.
     #
     # nodes - A Nokogiri::XML::NodeSet.