v2.0

Additions

• Added 2 new translators (GoogleTranslator2 and MicrosoftTranslator)
• Added text-to-speech support to almost all translators
• Added nullable annotations to the project

Changes

• Rewritten all the translators to use System.Text.Json
• Updated target frameworks to .NET Standard 2.0, 2.1 and .NET 6
• Updated the translators' constructors to make them DI-friendly
• Renamed Translator to AggregateTranslator
• Renamed Result property in favor of Translation and Transliteration properties