Make it easier to determine if Tor is being used or not

[ArrayBolt3]

Feature Request

Is your feature request related to a problem? Please describe.
Looking at the source code of this tool, I can see that it does support connecting to archive.is over Tor. However, the documentation in README.md is unclear, and I don't have a very good understanding of Go, so I can't tell under what circumstances Tor is used. There's also no switch that I can use to say "only use Tor, error out if Tor doesn't work, don't try to use normal HTTP(S)". As such, it's very difficult for a user without a decent understanding of Go to tell for sure whether Tor will be used. I tried using Wireshark to see what IPs were being contacted when using the archive.is CLI utility, and it appeared to be accessing my local Tor proxy, but also accessing the archive.ph website directly without Tor.

Describe the solution you'd like
Add a command-line argument to the archive.is CLI utility (and possibly in the internal Go API also) that allows forcing the use of Tor. (--force-tor might be a good name for the CLI argument.)

Describe alternatives you've considered
It might help to clarify the documentation in README.md, stating clearly when Tor is used and what the user can do to influence Tor's usage. This wouldn't allow a user to force the use of Tor and forbid the use of fallback methods however.

Teachability, Documentation, Adoption, Migration Strategy
./archive.is --force-tor https://example.com