Fixed: #186, #188, #189
Cleaned up lingering `.format()`s and replaced with appropriate f-strings.
Updated project structure to slightly more modern standards.
Enhanced flexibility when naming output files:
Example: `--template="%{artist}/%{album}/%{track}-%{title}" --space-char="_"`
Would produce "scene" style filenames.
Also added is the ability to:
- Retain upper case letters
- Leave spaces intact
- Convert characters to ASCII (北京 -> beijing)
- Allow additional characters like `()[];` etc