Publish CELOBTC pricing in Alfajores oracle

[albertclabs]

Expected Behavior

• New CELO/BTC price feed is published on Alfajores
• Contract is verified
• Public and devs are aware of how to interact with this feed. Short post to Discord?

Current Behavior

CELO/BTC price not supported in our Oracles. Us and the greater ecosystem cannot calculate what the Bitcoin price is and are unable to unlock advanced use cases of Bitcoin-like products.

Impact: Dapps like Moola will be able to price BTC and enable greater functionality for Celo users such as lending/borrowing of wrapped BTC.

Open questions:

• Additional cost to Oracles?
• Can we bundle this with implicit pairs work?

[nvtaveras]

Done, CELO/BTC oracles are now up on Alfajores and reporting. Here's a short write up on the oracle specs, including an example gist on how to interact with the oracles through contractkit:

https://docs.google.com/document/d/1XhRpomBhUSVFfsC3THxWVsLXsJ7MVkRKWJU9sFt7LbI/edit