FrontendCommon: Add PlaySoundAsync()

src/frontend-common/platform_misc.h

@@ -0,0 +1,10 @@
+#include "common/window_info.h"
+
+namespace FrontendCommon {
+void SuspendScreensaver(const WindowInfo& wi);
+void ResumeScreensaver();
+
+/// Abstracts platform-specific code for asynchronously playing a sound.
+/// On Windows, this will use PlaySound(). On Linux, it will shell out to aplay. On MacOS, it uses NSSound.
+bool PlaySoundAsync(const char* path);
+} // namespace FrontendCommon