Add compatibility with largebar mod.

[calloatti]

Largebar mod uses the top row of the player inventory to extend the hotbar to 18 slots, It would be great if randomblockplacement was aware of largebar and used the additional 9 slots as a source for the randomness.

gudenau/minecraft-largebar#3

[gbl]

This should be implemented in the 1.17-pre5 version.