feat: implement opacity to control visibility of subtitles (#3583)

* feat: implement opacity to control visibility of subtitles

implemented per discussion on https://github.com/react-native-video/react-native-video/issues/3579

updated docs and linked onTextTrackDataChanged to the subtitle style to clarify intent on how to control visibility.

* chore: update type so that we use a union of 0 1 vs any number

* chore: run ktlint to get rid of white spaces

* feat: add ability to have range of numbers for opacity; while, 0 will still not render the subtitles.

added util function for safeGetFloat

updated types

* feat: add ability to suppress subtitles with opacity 0

add data structure for subtitle styles for extensibility

* chore: run yarn check-ios

* chore: update documentation to clarify differences between android and ios

* Update android/src/main/java/com/brentvatne/exoplayer/ExoPlayerView.java

Co-authored-by: Olivier Bouillet <62574056+freeboub@users.noreply.github.com>

---------

Co-authored-by: Olivier Bouillet <62574056+freeboub@users.noreply.github.com>

ios/Video/Features/RCTPlayerObserver.swift

@@ -47,6 +47,8 @@ class RCTPlayerObserver: NSObject, AVPlayerItemMetadataOutputPushDelegate, AVPla
         }
     }
 
+    var subtitleStyle: SubtitleStyle?
+
     var playerItem: AVPlayerItem? {
         willSet {
             removePlayerItemObservers()
@@ -63,6 +65,7 @@ class RCTPlayerObserver: NSObject, AVPlayerItemMetadataOutputPushDelegate, AVPla
             playerItem.add(legibleOutput)
             metadataOutput.setDelegate(self, queue: .main)
             legibleOutput.setDelegate(self, queue: .main)
+            legibleOutput.suppressesPlayerRendering = subtitleStyle?.opacity == 0 ? true : false
         }
     }