[#98] nns: add `Version` method

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

nns/nns_contract.go

@@ -19,6 +19,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/interop/runtime"
 	"github.com/nspcc-dev/neo-go/pkg/interop/storage"
 	"github.com/nspcc-dev/neo-go/pkg/interop/util"
+	"github.com/nspcc-dev/neofs-contract/common"
 )
 
 // Prefixes used for contract data storage.
@@ -131,6 +132,11 @@ func Decimals() int {
 	return 0
 }
 
+// Version returns version of the contract.
+func Version() int {
+	return common.Version
+}
+
 // TotalSupply returns overall number of domains minted by the NeoNameService contract.
 func TotalSupply() int {
 	ctx := storage.GetReadOnlyContext()