Fixes#75
Enhance the email address conversion feature to filter suggestions based on partial domain inputs.
* Update `toEmailAddressCandidates` function in `Sources/KanaKanjiConverterModule/Converter/EmailAddress.swift` to filter suggestions based on the characters before '@'.
* Add logic to check if the input ends with '@' and filter the suggestions based on the characters before '@'.
* Generate suggestions for email domains that match the partial domain input.
* Add tests in `Tests/KanaKanjiConverterModuleTests/ConverterTests/EmailAddressConversionTests.swift` to verify the new filtering functionality for partial domain inputs like '@g' and '@y'.
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