Fetch a List of Firebase Documents with Firestore collectionData

We'll go through a quick intro to the 2 different types of data in Firestore: documents and collections. A document is an object and a collection is a list of documents.

Then we'll learn how to fetch a collection of documents from Firestore and display it in our application. We'll do this through API that Firestore offers us. In this case we'll call collectionData and pass in the collection function with a key of tasks that matches our collection in the Firestore.