Add support for requestBody `application/x-www-form-urlencoded`

[sergeysova]

      requestBody:
        content:
          application/x-www-form-urlencoded:
            schema:
              properties:
                name:
                  type: string
                  description: Updated name of the pet
                status:
                  type: string
                  description: Updated status of the pet

Use FormData for body