Extra params

[andreipoe]

Hi @rockymadden,

I've recently started using a self-hosted instance of transfer.sh and found your script to do exactly what I needed -- thanks for your work!

I've added a couple of small options to extend the functionality:

• The ability to set a custom URL to use your own server.
• A couple of handy aliases for upload and download to save on some typing.
• Parameters to support the custom expiry options of transfer.sh: max days and max downloads.

I'm making this pull request in case you think these are useful and you'd like to integrate them in the main version. I have another change, although that's more of a personal preference, so I'll open a separate pull request for that.

Thanks again for your work on transfer-cli and all the best to you.