fix: add ImageSource type to TypeScript (#51969)

Summary:
This PR adds ImageSource type to ImageSource.d.ts which is defined in Flow:

https://github.com/facebook/react-native/blob/d6f29c8afd14b2cc835649db3c59ed2f0e685331/packages/react-native/Libraries/Image/ImageSource.js#L87-L90

But not in the TypeScript file.

## Changelog:

[GENERAL] [FIXED] - add ImageSource type to TypeScript

Pull Request resolved: https://github.com/facebook/react-native/pull/51969

Test Plan: CI Green

Reviewed By: fabriziocucci

Differential Revision: D76532377

Pulled By: Abbondanzo

fbshipit-source-id: f1bbcd3b3fc07bb0f7e82f81ebaffedf9bc06148