Allowing circular references

Is there a way to generate the report allowing for circular dependencies on the parameters?

```
OpenApiDiffErrorImpl [VError]: ReferenceError: Circular $ref pointer found at /builds/#/components/schemas/Content/properties/children/items
at /usr/local/lib/node_modules/openapi-diff/dist/openapi-diff/spec-differ/diff-finder/json-schema-diff.js:27:15
at Generator.throw ()
at rejected (/usr/local/lib/node_modules/openapi-diff/dist/openapi-diff/spec-differ/diff-finder/json-schema-diff.js:6:65) {
jse_shortmsg: 'ReferenceError: Circular $ref pointer found at /builds/#/components/schemas/Content/properties/children/items',
jse_info: {},
code: 'OPENAPI_DIFF_DIFF_ERROR'
}
```

Thank you!

从报告循环 $ref 错误的 openapi-diff/dist/openapi-diff/spec-differ/diff-finder/json-schema-diff.js 开始，跟踪 Content schema 的比较过程。确定 /components/schemas/Content/properties/children/items 的预期行为，并将完成定义为：生成报告时不会因该循环引用而失败，同时为示例规范提供覆盖。

由索引模型根据 Issue 内容生成。