Add comprehensive type hints to all Python code

[dmort27]

Summary

This PR adds comprehensive type hints to all Python code in the epitran package, enhancing code readability, IDE support, and enabling static type checking.

Changes Made

Core Modules (20 files)

• Added type hints to all core modules in epitran/ package:
  • _epitran.py, simple.py, backoff.py, cedict.py, dictfirst.py
  • download.py, epihan.py, flite.py, ligaturize.py, meta.py
  • ppprocessor.py, puncnorm.py, reromanize.py, rules.py, space.py
  • stripdiacritics.py, tir2pp.py, vector.py, xsampa.py

Script Files (13 files)

• Added type hints to all script files in epitran/bin/ directory:
  • connl2engipaspace.py, connl2ipaspace.py, decompose.py, detectcaps.py
  • epitranscribe.py, isbijective.py, ltf2ipaspace.py, migraterules.py
  • reromanize.py, space2punc.py, testvectorgen.py, vie-tones.py
  • uigtransliterate.py (simple script with minimal changes needed)

Type Annotations Added

• Function parameters and return types: All functions now have proper type annotations
• Class methods: Enhanced with parameter and return type hints
• Complex data structures: Proper typing for dictionaries, lists, tuples, and nested structures
• Optional parameters: Used Optional[T] for nullable parameters
• Union types: Applied where multiple types are acceptable
• Callable types: Added for function parameters and callback handling

Typing Imports Used

• List, Dict, Tuple, Optional, Any, Union
• DefaultDict, Callable, Iterator, Set
• Specialized types for complex data structures

Benefits

1. Enhanced IDE Support: Better autocomplete, error detection, and refactoring capabilities
2. Static Type Checking: Enables use of tools like mypy for catching type-related bugs
3. Code Documentation: Type hints serve as inline documentation for function signatures
4. Maintainability: Easier to understand and maintain code with explicit type information
5. Python 3.10+ Compatibility: Modern type hinting practices aligned with current Python standards

Testing

• ✅ All core modules compile successfully
• ✅ Basic epitran functionality tested and working
• ✅ Script files compile and execute correctly
• ✅ No breaking changes to existing functionality
• ✅ Type annotations are syntactically correct

Compatibility

• Maintains full backward compatibility
• No runtime behavior changes
• Type hints are ignored by Python runtime, so no performance impact
• Compatible with Python 3.10+ as specified in project requirements

This work complements the earlier Python 2 to Python 3 modernization efforts and brings the codebase up to modern Python typing standards.