Add documentation for new attribute block toggle feature including:
- New commands: SCLToggleAttrBlock, SCLExpandAllAttrBlocks, SCLCollapseAllAttrBlocks
- New keybindings: <Leader>xa, <Leader>xae, <Leader>xac
- Feature description and usage example
- Add db_parser.lua to parse .db files (DATA_BLOCK with VAR sections)
- Update workspace_types.lua to scan for .db files in project
- Update blink_cmp_source.lua to provide DB auto-completion:
- DB names available in general completion (without quotes)
- Type quote to get DB members
- Multi-level nested member access support
- Add DB count to workspace commands
- Update README with Global DB documentation