Method with a list in result having the "object" type in the generated spec

[svetlyak40wt]

For example, for this code:

(uiop:define-package #:foo
  (:use #:cl))
(in-package #:foo)

(openrpc-server:define-api (test))

(openrpc-server:define-rpc-method (test foo) ()
  (:result list)
  (list "foo" "bar"))

this spec is generated:

FOO> (openrpc-server/discovery:generate-spec test)
(SERAPEUM:DICT
  "methods" '((SERAPEUM:DICT
                "name" "foo"
                "params" #()
                "result" (SERAPEUM:DICT
                           "name" "foo_result"
                           "schema" (SERAPEUM:DICT
                                      "type" "object"
                                      "properties" (SERAPEUM:DICT
                                                    )
                                      "required" #()
                                      "x-cl-class" "LIST"
                                      "x-cl-package" "COMMON-LISP"
                                     )
                          )
                "paramStructure" "by-name"
               ) )
  "openrpc" "1.0.0"
  "info" (SERAPEUM:DICT
           "title" "Default API"
           "version" "0.1.0"
          )
  "servers" '((SERAPEUM:DICT
                "name" "default"
                "url" "http://localhost:5000/"
               ) )
 ) 

but result should have schema with type = array.

Note, I've created this PR which adds generate-spec function used in the example: #17