implementations/similarity_calculator library

1. multi_language_search_engine package
2. documentation
3. implementations/similarity_calculator.dart

multi_language_search_engine package

1. Libraries
2. core/multi_language_search_engine
3. factory/search_engine_factory
4. implementations/arabic_normalizer
5. implementations/english_normalizer
6. implementations/similarity_calculator
7. interfaces/search_engine
8. multi_language_search_engine
9. multi_language_search_engine_method_channel
10. multi_language_search_engine_platform_interface
11. multi_language_search_engine_plugin