suggestion for the Cashtoken introspection opcodes

[mr-zwets]

The Cashtokens upgrade adds 6 new introspection opcodes, these would map cleanly to the following 6 new cashscript expressions. These are just a suggestion but might be helpful for other devs thinking already about new contracts enabled by the cashtokens upgrade

bytes tx.inputs[i].tokenCategory

bytes tx.inputs[i].nftCommitment

int tx.inputs[i].tokenAmount

bytes tx.outputs[i].tokenCategory

bytes tx.outputs[i].nftCommitment

int tx.outputs[i].tokenAmount