iOS Swift Conversion (#2527)

Converts iOS implementation from Objective-c to Swift

# During the conversion process some updates to the code structure were also made
- Modularize codebase from single file to smaller focused files
- Untangled large nested IF statements
- Added more null checks, since Swift is more strict with null pointers
- Added property to allow for decoding of local video sources with self contained key for offline playback
- Updates example apps to test react-native 0.63.4 and uses auto native dependency imports for android and ios

examples/basic/__tests__/App-test.js

@@ -0,0 +1,14 @@
+/**
+ * @format
+ */
+
+import 'react-native';
+import React from 'react';
+import VideoPlayer from '../src/VideoPlayer';
+
+// Note: test renderer must be required after react-native.
+import renderer from 'react-test-renderer';
+
+it('renders correctly', () => {
+  renderer.create(<VideoPlayer />);
+});