Helpers for third-party adaptors and middleware authors to generate route paths without even know the router that has being selected by user

Former-commit-id: b21147f2bc306d5c41539a1be0c83456c3d62651

adaptors/gorillamux/gorillamux.go

@@ -74,6 +74,9 @@ func New() iris.Policies {
 				// finally return the path given + the wildcard path part
 				return path + wildcardPart
 			},
+			Param: func(paramName string) string {
+				return "{" + paramName + "}"
+			},
 			// 	Note: on gorilla mux the {{ url }} and {{ path}} should give the key and the value, not only the values by order.
 			// 	{{ url "nameOfTheRoute" "parameterName" "parameterValue"}}.
 			//