Save config file after adding 'recent file'

* This has been bugging me for ages, it's not a problem typically for users
  as the config would be saved on shutdown, but if you're debugging
  renderdoc and you kill the process (by stopping debugging) after loading
  a log but before closing the program, the recent file wouldn't be saved!

renderdocui/Code/Core.cs

@@ -461,8 +461,13 @@ namespace renderdocui.Code
             }
 
             if (!temporary)
+            {
                 m_Config.AddRecentFile(m_Config.RecentLogFiles, logFile, 10);
 
+                if (File.Exists(Core.ConfigFilename))
+                    m_Config.Serialize(Core.ConfigFilename);
+            }
+
             m_FrameID = 0;
             m_EventID = 0;