Add API key to config file for explorer

[ccornick]

We should have API key support on token-driver (set in explorer mode). This way, we can have explorer-ui pass an API key to token-driver.

We do not want to have API key support on token-driver that is set in registry or client mode.

[brodoin]

@ccornick The climate explorer UI makes calls to climate-token-driver (running in explorer mode). It does not appear that climate-token-driver currently supports an API token. Should I also update climate-token-driver to have a configurable API key and then modify climate-explorer-ui to send the token along?

I could also just modify climate-explorer-ui to send the token along but we won't be able to verify it end-to-end until climate-token-driver implements the api key.

[brodoin]

Would estimate 2-4 hours including adding the parameter to the calls from climate-wallet.