Improve usability of settings on TV devices

* Add focus overlay to SettingsActivity
* Make screen "Contents of Main Page" navigable from remote

app/src/main/java/org/schabi/newpipe/settings/SettingsActivity.java

@@ -12,7 +12,9 @@ import android.view.Menu;
 import android.view.MenuItem;
 
 import org.schabi.newpipe.R;
+import org.schabi.newpipe.util.FireTvUtils;
 import org.schabi.newpipe.util.ThemeHelper;
+import org.schabi.newpipe.views.FocusOverlayView;
 
 
 /*
@@ -56,6 +58,10 @@ public class SettingsActivity extends AppCompatActivity implements BasePreferenc
                     .replace(R.id.fragment_holder, new MainSettingsFragment())
                     .commit();
         }
+
+        if (FireTvUtils.isFireTv()) {
+            FocusOverlayView.setupFocusObserver(this);
+        }
     }
 
     @Override

app/src/main/res/layout/list_choose_tabs.xml

@@ -12,6 +12,7 @@
     android:layout_marginTop="3dp"
     android:minHeight="?listPreferredItemHeightSmall"
     android:orientation="horizontal"
+    android:focusable="true"
     app:cardCornerRadius="5dp"
     app:cardElevation="4dp">