Add .mka to file extensions.

Fixes issue #2569

src/widgets/fileview.cpp

@@ -32,7 +32,7 @@
 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 "
-                                    "*.oga";
+                                    "*.oga *.mka";
 
 FileView::FileView(QWidget* parent)
     : QWidget(parent),