Add RecentlyChanged()

[veechs]

What will your feature request solve?

In some scenarios such as master looter, It can be useful to pull all newly acquired items into the same Group.

Describe the solution you'd like

Add a RecentlyChanged() rule function. It should probably take New/Up/Down parameters.

Describe alternatives you've considered

The existing Highlight New feature gets most of the way there, but still requires some scanning around the inventory instead of having everything in one place.

Additional context

Requested by @melbaa.