Update Contract and Application API docs for Fabric Gateway (#3048)
Update Contract and Application API docs for Fabric Gateway (#3048)

Signed-off-by: Mark S. Lewis <ff7eb00f821c62e10b8e7cdcfd5b1b671f59d90e@uk.ibm.com>
jimthematrix/fabric,hyperledger/fabric,manish-sethi/fabric,jimthematrix/fabric,manish-sethi/fabric,hyperledger/fabric