Improved Captions handling

New options for captions in `Settings-Player`:

- Always show captions
- Default language

User can now select whether they want to show captions automatically when the video starts, and select the language.

Captions selector now shows proper name -> `English (en)` instead of only `en`

Model/Player/Backends/MPVBackend.swift

@@ -217,9 +217,15 @@ final class MPVBackend: PlayerBackend {
         #endif
 
         var captions: Captions?
-        if let captionsLanguageCode = Defaults[.captionsLanguageCode] {
-            captions = video.captions.first { $0.code == captionsLanguageCode } ??
-                video.captions.first { $0.code.contains(captionsLanguageCode) }
+
+        if Defaults[.captionsAutoShow] == true {
+            let captionsLanguageCode = Defaults[.captionsDefaultLanguageCode]
+            if !captionsLanguageCode.isEmpty {
+                captions = video.captions.first { $0.code == captionsLanguageCode } ??
+                    video.captions.first { $0.code.contains(captionsLanguageCode) }
+            }
+        } else {
+            captions = nil
         }
 
         let updateCurrentStream = {
@@ -254,9 +260,8 @@ final class MPVBackend: PlayerBackend {
 
                 self.startClientUpdates()
 
-                // Captions should only be displayed when selected by the user,
-                // not when the video starts. So, we remove them.
-                self.client?.removeSubs()
+                if Defaults[.captionsAutoShow] { self.client?.setSubToAuto() } else { self.client?.setSubToNo() }
+                PlayerModel.shared.captions = self.captions
 
                 if !preservingTime,
                    !upgrading,

Model/Player/Backends/MPVClient.swift

@@ -405,6 +405,14 @@ final class MPVClient: ObservableObject {
         setString("video", "no")
     }
 
+    func setSubToAuto() {
+        setString("sub", "auto")
+    }
+
+    func setSubToNo() {
+        setString("sub", "no")
+    }
+
     var tracksCount: Int {
         Int(getString("track-list/count") ?? "-1") ?? -1
     }