Add exiting UI animation

[bhiltune]

Add exiting UI animation

[onesounds]

I had built this but decided not to apply it. It creates a delay while the animation is running (the user has to wait for the animation to finish) and feels very awkward to use.

The animation was intended to be an easy way to recognize the position of the window. (Exit animations do not fall under this intent.) Since Flow is not a normal window, there are some issues with applying normal methods to it. I'm also considering removing some of the animations that currently exist.

Personally, I prefer a nice-looking program, even if it's a bit inconvenient, so I think your opinion is worth considering. I'll consider it once the current priority issues (translucent windowing, etc.) are resolved.

However, it would be inconvenient in the current implementation and we have no plans for it in the near term, so I'll closing this issue.