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

package.json

@@ -1,6 +1,6 @@
 {
     "name": "react-native-video",
-    "version": "5.2.0",
+    "version": "6.0.0-alpha1",
     "description": "A <Video /> element for react-native",
     "main": "Video.js",
     "license": "MIT",
@@ -43,7 +43,8 @@
         "shaka-player": "^3.3.2"
     },
     "scripts": {
-        "lint": "eslint ."
+        "lint": "yarn eslint .",
+        "xbasic": "yarn --cwd examples/basic"
     },
     "files": [
         "android-exoplayer",