Provide a way to use an existing CMMotionManager

## Issue

According to[ Apple's docs](https://developer.apple.com/documentation/coremotion/cmmotionmanager) for `CMMotionManager`, only a single object should exist for the app:

> **Important**
>
> Create only one [CMMotionManager](https://developer.apple.com/documentation/coremotion/cmmotionmanager) object for your app. Multiple instances of this class can affect the rate at which data is received from the accelerometer and gyroscope.

If an app already uses `CMMotionManager` and imports this library, it could potentially cause side effects with the one in [`AppLogosScene`](https://github.com/Automattic/AutomatticAbout-Swift/blob/0f784591b324e5d3ddc5771808ef8eca923e3de2/Sources/AutomatticAbout/AutomatticAppLogosCell.swift#L113). Perhaps an existing `CMMotionManager` could be supplied to this library.

## Context

We use gyro data for the Jetpack app landing screen which requires a [`CMMotionManager` object](https://github.com/wordpress-mobile/WordPress-iOS/blob/72e204de112edc91cdbe2a87809c2a3bf572e414/WordPress/Jetpack/Classes/NUX/JetpackPrologueViewController.swift#L20).

Start in Sources/AutomatticAbout/AutomatticAppLogosCell.swift at the AppLogosScene CMMotionManager usage, then compare it with the JetpackPrologueViewController example linked in the issue. Define how an existing CMMotionManager can be supplied without changing current behavior, and confirm that the library uses the supplied manager rather than creating a second instance.

Written by the indexing model from the issue text.