Warn user when recording with Windows game mode on

[jetstream96]

I think it would be very helpful to show a pop up windows to warn user when they click stream, record, or replay buffer with Windows game mode on. A few days ago I was recording while the game mode is on, and the footage recorded was very choppy. I spent an hour trying different settings, but it's still the same. If there is a feature like this, it would save a lot of time for clueless people like me who did not realize game mode can significantly impact the performance of OBS.

What do you think about this? I can try to submit a PR if you think this feature can be added.

Thanks for your great software.