Fix android api

[arashi-dev]

Hi there!

As I promised here #19, I didn't disappear! and I may create much more PR in future, since we really need this library for our apps!

For now, I only fixed open, read_binary and write_binary commands for android. I didn't test other commands but they may also work. I am still working on it during our app development. I thought it would be better to make this PR, so that you can also contribute and give suggestions (including coding style (code refactoring is really needed, for the new changes)).

Future plans:

• Fix more commands (if needed in our app)
• Add unit tests (should I add here or on separate PR?)
• We are using this library with https://github.com/slowtec/tokio-modbus and it forced us to make a custom struct with AsyncWrite and AsyncRead traits to make an adapter for tauri-plugin-serialport. and we may need it in other apps we are developing. so this should be published as a tauri library that uses tauri-plugin-serialplugin as nested dependency. OR, we may add it here as a feature to tauri-plugin-serialplugin🤔 I will be very thankful if you checkout this gist and give us your feedback on where to publish it (https://gist.github.com/arashi-dev/89b31ef7b86ebb3ef856a6334366adad)

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[s00d]

Hi, thanks a lot for the work you’ve done! I’ve merged and released version v2.21.1. Unfortunately, I can’t test it right now - I’ll need to find suitable hardware first.