Improve logging and add test case

[binarykitchen]

A first attempt to improve logging, refer to https://github.com/ChetanXpro/nodejs-whisper/issues/114

With this change:

• Remove verbose option
• Log levels are introduced, and thus there is less noise in consoles, especially for production
• You can pass over any custom logger, like Pino
• The default logger is set to Node.js console
• Adds missing dev dependency nodemon
• Adds missing .gitmodules for subproject cpp/whisper.cpp

And a nice bonus, adds an example script for easier testing with an example wav file :)