Ability to change the mouse cursor

Dear ImGui has a function to set the mouse cursor but it's not exposed by DPG.

This feature was discussed in the Discord group (see [link](https://discord.com/channels/736279277242417272/1173714948300488764/1174275325207789578)). The lack of ability to change the mouse cursor was a drawback when trying to create a custom adjustable splitter widget (similar to adjustable columns in tables).

User v-ein suggested:

> [Such a function] would need to be bound to a widget, so that when the widget is hovered, mouse cursor changes. Not much work, but we can't add it to every widget, that would be a mess. It could be, for example, an argument to dpg.group, since a group is a pretty much universal container - we can wrap virtually anything with a group.