[Library Manager] Please add arduino-async-duplex and arduino-async-modem

[coddingtonbear]

I've recently created a couple libraries that might be useful for folks interacting with devices requiring call-and-response style commands (like the AT commands so commonly used by GSM/LTE modems); if you wouldn't mind, could you please add the following two libraries to the Library Manager?

• https://github.com/coddingtonbear/arduino-async-modem
• https://github.com/coddingtonbear/arduino-async-duplex

Cheers!

[cmaglie]

Done!