v1.2.0

- Added `Line` option to subtitle generation modes, allowing subtitles to be generated based on line breaks in the text, by @mleg in #94.
- Added a loading indicator to the book handler window for better user experience during book preprocessing.
- Fixed `cannot access local variable 'is_narrow'` error when subtitle format `SRT` was selected, mentioned by @Kinasa0096 in #88.
- Fixed folder and filename sanitization to properly handle OS-specific illegal characters (Windows, Linux, macOS), ensuring compatibility across all platforms when creating chapter folders and files.
- Fixed `/` and `\` path display by normalizing paths.
- Fixed book reprocessing issue where books were being processed every time the chapters window was opened, improving performance when reopening the same book.
- Fixed taskbar icon not appearing correctly in Windows.
- Fixed “Go to folder” button not opening the chapter output directory when only separate chapters were generated.
- Improvements in code and documentation.