Using `x-express-openapi-disable-validation-middleware` extension

[Daniel Gruszczyk]

In your docs and sample project a x-express-openapi-disable-validation-middleware can be added at a top-level api-doc.

However! Configuring top-level api-doc like so in TypeScript results in an error:

Object literal may only specify known properties, and ''x-express-openapi-disable-validation-middleware'' does not exist in type 'Document<{}>'.ts(2353)
(property) 'x-express-openapi-disable-validation-middleware': boolean

Code to reproduce - just use schema with the mentioned vendor extension:

import { OpenAPIV3 } from 'openapi-types'

export const schema: OpenAPIV3.Document = {
  openapi: '3.1.0',
  info: {
    title: 'My API',
    version: '1.0.0',
    description:
      'whatever service'
  },
  paths: {},
  'x-express-openapi-disable-validation-middleware': true
}

The initialize function accepts OpenAPIV3.Document, but this in turn has some props described here missing:
https://github.com/kogosoftwarellc/open-api/blob/main/packages/openapi-types/index.ts#L271