Custom vendor bag drag&drop

[FunnyMan3595]

What Does This PR Do

You can now dump the contents of a bag (or serving tray) into a custom vendor by dragging it from your hand onto the vendor.

Why It's Good For The Game

It's nice to have a better way to load custom vendors when you have a bunch of matching items, e.g. freshly-cooked food.

Testing

Clicked an unlocked custom vendor with a serving tray. Was prompted for a price for the tray.
Dragged the tray onto the vendor. Was prompted for a price for its contents.
Did a bunch of permutations of stuff in the bag already being in the vendor or not and doing all the things that should prevent it from succeeding or continuing.

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Declaration

• I confirm that I either do not require pre-approval for this PR, or I have obtained such approval and have included a screenshot to demonstrate this below.

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Changelog

🆑
add: You can now dump the contents of a bag (or serving tray) into a custom vendor by dragging it from your hand onto the vendor.
/:cl: