Restructure BarcodeScanner API reference with individual property headings

- Replace tables with #### headings for all config properties (BarcodeScannerConfig, ScannerViewConfig, ResultViewConfig, etc.)
- Each property now has its own anchor for direct linking
- Add missing barcodeImage property to BarcodeScanResult
- Fix incorrect optional marker on status property
- Update intro to align with user guide messaging

Author: Tom-Dynamsoft