-Added display name to subtitles that resolves language code into locale.

src/main/java/org/schabi/newpipe/extractor/Subtitles.java

@@ -3,8 +3,11 @@ package org.schabi.newpipe.extractor;
 import org.schabi.newpipe.extractor.stream.SubtitlesFormat;
 
 import java.io.Serializable;
+import java.util.Locale;
 
 public class Subtitles implements Serializable {
+    private final static String AUTO_GENERATED_TAG = " (auto-generated)";
+
     private final SubtitlesFormat format;
     private final String languageCode;
     private final String URL;
@@ -30,4 +33,9 @@ public class Subtitles implements Serializable {
     public boolean isAutoGenerated() {
         return autoGenerated;
     }
+
+    public String getDisplayName() {
+        final Locale locale = new Locale(languageCode.replace("-", "_"));
+        return locale.getDisplayLanguage() + (isAutoGenerated() ? AUTO_GENERATED_TAG : "");
+    }
 }