editor: Add comment_on_empty_lines setting for multi-line comment toggle

[NsdHSO]

This addresses #60738 — when toggling comments on a multi-line selection, empty lines are skipped instead of getting comment markers.

Adds a new setting comment_on_empty_lines (default: false). When enabled, blank lines within the selection also receive // at the minimum ind

entation column, matching VS Code behavior.

Changes:

• New ToggleCommentOnEmptyLines action + toggle handler in config.rs
• New comment_on_empty_lines field in EditorSettings
• Blank line handling in toggle_comments() — inserts comment prefixes with proper indentation alignment, handles empty lines (padded) and whitespace-only lines
• VSCode import mapping
• Settings schema + default in default.json
  Video for better
  https://github.com/user-attachments/assets/cb4f2ac9-a728-4b54-8517-9d08b898a92e
  https://github.com/user-attachments/assets/68f6f179-85bd-4df2-99a0-bd086fe5b038

Release Notes:

• Added comment_on_empty_lines setting to include blank lines when toggling comments in multi-line selections