Support for SnapshotOptions

[robokozo]

What problem is this solving

When $binding to a query that contains serverTimestamp() the timestamp property will return null as described here: firebase/firebase-js-sdk#1929 (comment)

The solution suggested in the post is to include https://firebase.google.com/docs/reference/js/firebase.firestore.SnapshotOptions.html

Which can be applied to the .get({ serverTimestamps: "previous" }) or the .data({ serverTimestamps: "estimate" }) on the snapshot.

Proposed solution

Allow the user to pass down the snapshotOptions when setting up a $bind

Describe alternatives you've considered

Add additional logic around the code that consumes the data to expect the first response to include null

[pmalbu]

Has any progress been made on this? It seems like a fairly easy feature to add. It would be really nice to get rid of my v-if="field.created" logic 🙏🏻
I would love to make the change myself and submit a PR but I'm concerned I'd screw something else up in the package... 🙈

[posva]

Implemented in 76d36f5