Add .oga to file extensions.

Fixes issue #3180

src/widgets/fileview.cpp

@@ -31,7 +31,8 @@
 
 const char* FileView::kFileFilter = "*.mp3 *.ogg *.flac *.mpc *.m4a *.aac *.wma "
                                     "*.mp4 *.spx *.wav *.m3u *.m3u8 *.pls *.xspf "
-                                    "*.asx *.asxini *.cue *.ape *.wv *.mka *.opus";
+                                    "*.asx *.asxini *.cue *.ape *.wv *.mka *.opus "
+                                    "*.oga";
 
 FileView::FileView(QWidget* parent)
     : QWidget(parent),