add missing file

src/plugins/secondary_backends/sound/CMakeLists.txt

@@ -0,0 +1,18 @@
+find_package(Qt5Multimedia QUIET)
+set_package_properties(Qt5Multimedia PROPERTIES
+                                    PURPOSE "Support for sound Notifications"
+                                    TYPE OPTIONAL)
+if(Qt5Multimedia_FOUND)
+    qt5_wrap_ui(UI soundsettings.ui)
+
+    set( SOUND_SRC
+        sound.cpp
+        soundsettings.cpp
+        ${UI}
+        )
+
+    add_library(libsnore_secondary_backend_sound MODULE ${SOUND_SRC} )
+    target_link_libraries(libsnore_secondary_backend_sound Snore::Libsnore Qt5::Multimedia)
+
+    install(TARGETS libsnore_secondary_backend_sound ${SNORE_PLUGIN_INSTALL_PATH})
+endif()

src/plugins/secondary_backends/sound/plugin.json

@@ -0,0 +1 @@
+{ "type" : "secondary_backend", "name" : "Sound" }