Add Tests to Bot vyper repos

[verabehr]

Add tests to the following repos, so they can be audited.

Add the details of how to run the tests in the readme

• [ ] https://github.com/VolumeFi/curve-limit-order-bot-vyper
• [ ] https://github.com/VolumeFi/curve-twap-bot-vyper
• [ ] https://github.com/VolumeFi/offramp-eure-bot

[verabehr]

@webelf101 FYI - here are the requirements for test from our auditors https://docs.google.com/document/d/10_t7Kt814Otp-FMFK8mvCsxb3tX3wyu1Z9V4nhZxTY8/edit#heading=h.7lbrpb7hdwvw