Add API_KEY to CI environment

[RyanZim]

Need to have an API key on the CI server in order to run some tests there. Relevant code:

https://github.com/ExodusMovement/cryptocompare/blob/6b2cc44b35952ede00d728953e95ae0eb95981e7/test/cryptocompare.test.js#L7-L14

https://github.com/ExodusMovement/cryptocompare/blob/6b2cc44b35952ede00d728953e95ae0eb95981e7/test/cryptocompare.test.js#L278