Add Redis

[johncmanuel]

Description

While running test cases (see #10), I've noticed that the API endpoint, /api/images, tends to throw 500-related errors (see below). There are multiple causes for this, where one is the logic for fetching images. The other is making too many calls to Google's API.

Solution

I propose we use Redis to alleviate our API and Google's API. This would not only speed up our application but prevent repeated calls to Google's API and thus save on potential costs.

[johncmanuel]

Upstash provides a serverless Redis instance with a nice free tier. Experimentations with Upstash will be conducted sometime in the future.