feat: now playing chapter track

ios/App/Shared/models/PlaybackSession.swift

@@ -160,3 +160,11 @@ class PlaybackSession: Object, Codable, Deletable {
         try container.encode(localMediaProgressId, forKey: .localMediaProgressId)
     }
 }
+
+extension PlaybackSession {
+    func getCurrentChapter() -> Chapter? {
+        return chapters.first { chapter in
+            chapter.start <= self.currentTime && chapter.end > self.currentTime
+        }
+    }
+}

ios/App/Shared/models/PlayerSettings.swift

@@ -12,6 +12,8 @@ class PlayerSettings: Object {
     // The webapp has a persisted setting for playback speed, but it's not always available to the native code
     // Lets track it natively as well, so we never have a situation where the UI and native player are out of sync
     @Persisted var playbackRate: Float = 1.0
+    @Persisted var chapterTrack: Bool = true
+
     
     // Singleton pattern for Realm objects
     static func main() -> PlayerSettings {

ios/App/Shared/models/server/Chapter.swift

@@ -39,3 +39,13 @@ class Chapter: EmbeddedObject, Codable {
         try container.encode(title, forKey: .title)
     }
 }
+
+extension Chapter {
+    func getRelativeChapterCurrentTime(sessionCurrentTime: Double) -> Double {
+        return sessionCurrentTime - self.start
+    }
+
+    func getRelativeChapterEndTime() -> Double {
+        return self.end - self.start
+    }
+}