[Feature Request] Add support for Nautical Miles (nmi)

[deepjyoti30]

Hey there, pretty useful tool. I currently use this in one of my projects. I would like to request you to add support for Nautical Miles nmi.

You can refer to this to see how to convert between km and nmi as an example.

[bosix]

Hi @deepjyoti30 @bcicen , I've just create a pull request to add the new unit. Just let me know if you want me anthing to change.

Regards