Update Slot on Shift Click

[ferriarnus]

Description

Shift Clicking an item calls the slot.setChanged method, however, it does not call onContentChanged as it should as well. This PR solves that by using slot.set instead of directly changing the itemstack.

Closes #445

Todo

• Things that are yet to be completed for this PR to no longer be a draft.

Checklist:

• My code follows the style guidelines of this project (.editorconfig, most IDEs will use this for you).
• I have performed a self-review of my own code.
• I have commented my code in areas it may be challenging to understand.
• I have made corresponding changes to the documentation.
• My changes are ready for review from a contributor.

[Rover656]

I will trust that this works, but looks like it makes sense. Cheers!