Feature: Create a pipe in Angular Fire that extends the Angular Date for formatting firebase doc timestamps

### Version info

**Angular:** 14.2.6

**Firebase:** 11.2.0

**AngularFire:** latest

**Other (e.g. Ionic/Cordova, Node, browser, operating system):**

### Expected behavior
Today at the firebase summit, @davideast had a really nice presentation with Angular and Firebase. We discussed that it would be awesome to have an Angular pipe in AngularFire that could extend the Angular Pipe so we don't have to use the `.toDate()` method in an Angular service (because of formatting), or use `.toDate()` directly in the template (would trigger on every rerender). So a Pipe would be awesome.

### Actual behavior
No AngularFire Pipe exists to format Firebase Document timestamps.

No implementation files or tests are named. Start by locating AngularFire's public pipe exports and existing timestamp-related handling, then verify how Angular templates currently format Firebase document timestamps. Done means an exported Angular pipe formats those timestamps without requiring .toDate() in a template or service, with coverage for the intended behavior.

索引モデルが issue の本文から書いたものです。