Speech synthesis does not handle non-Latin text when the locale is set to English

If you have, for example, a Korean road name, speech synthesis using `AVSpeechSynthesizer` skips straight over this.

I assume that this is fixable with better annotation of the voice instructions text from Valhalla / construction of the utterances on the iOS side.

I would not be surprised if this is also an issue on Android using the default TTS engine.