Background color unchanged

Keep the background color unchaged on Windows console when using colored loggers.

include/spdlog/sinks/wincolor_sink.h

@@ -80,7 +80,11 @@ private:
     {
         CONSOLE_SCREEN_BUFFER_INFO orig_buffer_info;
         GetConsoleScreenBufferInfo(out_handle_, &orig_buffer_info);
-        SetConsoleTextAttribute(out_handle_, attribs);
+        WORD back_color = orig_buffer_info.wAttributes;
+        // retrieve the current background color
+        back_color &= ~(FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE | FOREGROUND_INTENSITY);
+        // keep the background color unchanged
+        SetConsoleTextAttribute(out_handle_, attribs | back_color);
         return  orig_buffer_info.wAttributes; //return orig attribs
     }
 };