Add operation to get a list of supported languages for recognition / alignment / translation engines

[rotemdan]

Related to discussion in #53

Unfortunately, no cloud speech-to-text provider has an API method to retrieve the supported language list. They have some online resources, but they are not in a machine readable format.

To provide this kind of a feature, I need to manually collect the information and encode it in a machine-readable format. The information may not stay accurate since there's no automated way to continuously keep it up-to-date.

Online resources

• Google Cloud STT language list
• Amazon Transcribe language list
• Microsoft Azure STT language list
• Microsoft Azure speech translation language list
• Whisper / whisper.cpp / OpenAI Cloud STT language list (only lists languages with less than 50% word error rate)

Supported languages for offline engines

• dtw alignment: all languages supported by the eSpeak-NG speech synthesizer
• dtw-ra alignment: all languages supported by the recognition engine used (typically Whisper)