Run unit tests on CI, fix InitialWindowSafeAreaInsets with jest and add tests for it

package.json

   "license": "MIT",
   "scripts": {
     "start": "react-native start",
-    "test": "yarn validate:prettier && yarn validate:eslint && yarn validate:typescript",
+    "test": "yarn validate:prettier && yarn validate:eslint && yarn validate:typescript && yarn validate:jest",
     "validate:eslint": "eslint \"src/**/*.{js,ts,tsx}\" \"example/**/*.{js,ts,tsx}\"",
     "validate:typescript": "tsc --project ./ --noEmit",
     "validate:prettier": "prettier \"src/**/*.{js,ts,tsx}\" \"example/**/*.{js,ts,tsx}\" --check",

src/InitialWindowSafeAreaInsets.ts

   // eslint-disable-next-line @typescript-eslint/no-explicit-any
 ) as any;
 
-export default (RNCSafeAreaViewConfig.Constants != null
+export default (RNCSafeAreaViewConfig != null &&
+RNCSafeAreaViewConfig.Constants != null
   ? RNCSafeAreaViewConfig.Constants.initialWindowSafeAreaInsets
   : null) as EdgeInsets | null;

src/__tests__/index-test.tsx

 import * as React from 'react';
 import * as ReactTestRenderer from 'react-test-renderer';
-import { View } from 'react-native';
+import { View, UIManager } from 'react-native';
 import { SafeAreaProvider, SafeAreaView, useSafeArea } from '../index';
 import NativeSafeAreaView from '../NativeSafeAreaView';
 
     expect(component).toMatchSnapshot();
   });
 });
+
+describe('initialWindowSafeAreaInsets', () => {
+  it('is null when no view config is available', () => {
+    jest.resetModules();
+    expect(require('../index').initialWindowSafeAreaInsets).toBe(null);
+  });
+
+  it('it uses the constant provided by the view config', () => {
+    jest.resetModules();
+    const testInsets = {
+      top: 20,
+      left: 0,
+      right: 0,
+      bottom: 0,
+    };
+    UIManager.getViewManagerConfig = jest.fn(name => {
+      if (name === 'RNCSafeAreaView') {
+        return {
+          Commands: {},
+          Constants: {
+            initialWindowSafeAreaInsets: testInsets,
+          },
+        };
+      }
+      return { Commands: {} };
+    });
+
+    expect(require('../index').initialWindowSafeAreaInsets).toBe(testInsets);
+    expect(UIManager.getViewManagerConfig).toBeCalledWith('RNCSafeAreaView');
+  });
+});