Add terms ack and onboarding to bidbot setup steps

[andrewxhill]

It would be nice that while auctions are still experimental, we have a better line of contact with providers running the network. Additionally, bidbot is providing enough benefit to providers at this point in time, that we should also ask them to commit to providing free retrieval for all deals they store from the system. So:

Update Readme.

I think we can more or less copy the language from here: https://github.com/filecoin-project/filecoin-discover-dealer#terms-and-eligibility

Update bidbot setup

It would be nice if bidbot required any provider to do 2 things before they submit their first bid.

1. Ack a terminal print out of the above terms.
2. Submit an email address in the terminal that we can collect and use for technical communication (probably requiring confirmation that we can use it that way at the same time)