query schema at least has one 'required' item about koa-oai-router HOT 1 CLOSED

I'm using Json-Schema to validate parameters, but Json-Schema says:

required:
The value of this keyword MUST be an array. This array MUST have at least one element. Elements of this array MUST be strings, and MUST be unique.
An object instance is valid against this keyword if its property set contains all elements in this keyword's array value.

But OAI not validate query parameters through Json-Schema. Query could be no parameter.
So i inject a default required key koa-oai-router:default:required:just4validatequery for query if it's schema has no required field.
PR #7

from koa-oai-router.