Add type for export object in AssetRegistry (#48734)

Summary:
Pull Request resolved: #48734

Changelog:
[General][Changed] - Added type for exported object in AssetRegistry

Reviewed By: cortinico

Differential Revision: D68272679

fbshipit-source-id: 1202009f886b2d35528009a3ac58aab24af9ef82

Author: coado

packages/react-native/Libraries/Image/AssetRegistry.js

@@ -10,4 +10,9 @@
 
 'use strict';
 
-module.exports = require('@react-native/assets-registry/registry');
+import type {PackagerAsset} from '@react-native/assets-registry/registry';
+
+module.exports = require('@react-native/assets-registry/registry') as {
+  registerAsset: (asset: PackagerAsset) => number,
+  getAssetByID: (assetId: number) => PackagerAsset,
+};

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -4721,7 +4721,10 @@ declare export default typeof EventPolyfill;
 `;
 
 exports[`public API should not change unintentionally Libraries/Image/AssetRegistry.js 1`] = `
-"declare module.exports: $FlowFixMe;
+"declare module.exports: {
+  registerAsset: (asset: PackagerAsset) => number,
+  getAssetByID: (assetId: number) => PackagerAsset,
+};
 "
 `;