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/httprouter/httprouter.go

@@ -545,6 +545,9 @@ func New() iris.Policies {
 				// finally return the path given + the wildcard path part
 				return path + wildcardPart
 			},
+			Param: func(paramName string) string {
+				return string(parameterStartByte) + paramName
+			},
 			// path = "/api/users/:id", args = ["42"]
 			// return "/api/users/42"
 			//