added diva/usd feed (coingecko)

[0xSpuddy]

Summary

This PR adds a DIVA/USD spot price feed based on coingecko price.

Steps Taken to QA Changes

test report on mumbai: https://mumbai.polygonscan.com/tx/0xf5fa04a8e552449e27887d4a139c92b7b0ef73232c19e556a989df7eed49be09

This pull request is:

• [x] A feature implementation
  • closes issue #706