Invalid TS return type for `getDeviceId()`

Hi,

While browsing the docs, I encounter the following sentence:

> You can retrieve the Device ID that Amplitude uses with Amplitude.getInstance().getDeviceId(). This method can return null if a Device ID has not been generated yet.

However, the types list it as returning a string: https://github.com/amplitude/Amplitude-ReactNative/blob/183a6b0669abe651bf47b08833a2e4d3c0a64552/src/types.ts#L27

Shouldn't this be changed to `getDeviceId(instanceName: string): Promise;`?