Add support to transfer.sh

[nikitavoloboev]

Would be quite neat if you could specify that as option. :)

The website.

[a-ungurianu]

Transfer.sh should work now. You'll have to use the --provider transfer-sh as a flag to force it to upload to it

Will come up with a way to config your preferred providers for specific files ASAP

[a-ungurianu]

Leaving this open until we send the change to npm