CLI tool to easily securely transfer files between computers

Probably with a tiny service running on the internet to ease pairing of the machines.

Something like:

```sh
# Machine A:
$ npx share .env
Run on the other machine:
$ npx share pull 1234ABC
Waiting for remote machine to join...

# Machine B:
$ npx share pull 1234ABC
Connected. Downloading file .env (350 B)...

```

## Technical considerations
- Need service to allow machines to find eath other by nothing more than a short temporary ID
- Need UPNP or something similar to allow incoming connections on any device (-> main traffic is p2p)
- Might be able to use STUN for that ()

## Potential advanced features
- Share / pull by contact name
- Create an identity file (key pair) on first run (or maybe just use SSH key pair)
- Allow importing public keys using a friendly name into a contact list
- Much securer, more convenient if you imported the other person's key already
- Log into organization account to sync contacts

## Prior art
- (Python tool)
- (Need to encrypt yourself)