move audio files to src/audio

a

src/audio/README.md

@@ -0,0 +1,3 @@
+Code to support GD's internal/external audio players.
+
+Only `audioplayerinterface.hh` is supposed to be used outside this folder.

src/ui/articleview.hh

@@ -10,7 +10,7 @@
 #include <QWebEngineView>
 #include <list>
 #include "article_netmgr.hh"
-#include "audioplayerinterface.hh"
+#include "audio/audioplayerinterface.hh"
 #include "instances.hh"
 #include "groupcombobox.hh"
 #include "globalbroadcaster.hh"

src/ui/mainwindow.hh

@@ -14,7 +14,7 @@
 #include "config.hh"
 #include "dict/dictionary.hh"
 #include "article_netmgr.hh"
-#include "audioplayerfactory.hh"
+#include "audio/audioplayerfactory.hh"
 #include "instances.hh"
 #include "article_maker.hh"
 #include "scanpopup.hh"