Create a document to setup Airtable

[mihok]

Currently the application requires Airtable to run some parts of the application, but there is no instructions on how to obtain an API Key from the service. Lets write a airtable.md text document to explain how to go about adding Airtable to the project so developers joining in can quickly get set up.

Stretch Goal

After Airtable is set up the service expects a "Base" (Airtable's word for a set of database tables) to be set up on Airtable with specific tables in that Base.

[oizabaiye]

I'd like to work on this as well - though I expect it should be done before tackling the Readme? Shall we discuss what makes sense to start with first?

[oizabaiye]

Latest commit on the pull request should have the readme for Airtable. I added some temporary error handling wrt the Fetch request in Entity.js (lines 23 - 24). There's probably a better way to handle the empty response.