Add x-api-key to search call

[mbifulco]

Describe your PR

This PR adds an x-api-key parameter to our calls to the search endpoint

Fixes #311

Pages/Interfaces that will change

/businesses search page

Screenshots / video of changes

This will appear in the network tab of your browser dev tools when you execute a search (highlighted here). I'll need confirmation from @elchris that this is what we're looking for, since the API changes aren't deployed yet.

Steps to test

1. @elchris help! :)

Additional notes

• [x] Q: do we make any other API calls to our own endpoints? I couldn't find any.
• [ ] I'd like to implement react-query to better cache search calls on the front end at some point (that should maybe be broken out into its own issue?)

[mbifulco]

@elchris I'm going through the checklist in #311 to get this done, and I see reference to a staging environment... do we have/use a staging environment? I don't recall ever using one for the website.

If we don't, this is ready to merge - the correspomding API key is on netlify for the production environment

[magnificode]

@mbifulco feel free to add an issue for the react-query stuff. That seems like a great addition!