Validation too strict for stylesheet and scripts

[teikjun]

🐛 Bug Report

The validation for stylesheets does not accept unknown fields.
The validation for scripts does not accept both defer and async.
As noted in this article, if you specify both, async takes precedence on modern browsers, while older browsers that support defer but not async will fallback to defer. So, it is valid to have both.

Have you read the Contributing Guidelines on issues?

Yes

To Reproduce

1. Use the following config in docusaurus.config.js (this config comes from a user on discord):

  stylesheets: [
    {
      href: '/katex/katex.min.css',
      type: 'text/css',
      integrity:
        'sha384-zB1R0rpPzHqg7Kpt0Aljp8JPLqbXI3bhnPWROx27a9N0Ll6ZP/+DiW/UqRcLbRjq',
      crossorigin: 'anonymous',
    },
  ],
  scripts: [
    {
      src: `/analytics.js`,
      async: true,
      defer: true,
    },
  ],

2. You should get the following error:

Error: "scripts[0]" does not match any of the allowed types
"stylesheets[0]" does not match any of the allowed types

Expected behavior

This should pass the validation.

Actual Behavior

ValidationError raised.

Your Environment

• Docusaurus version used: alpha.59
• Environment name and version (e.g. Chrome 78.0.3904.108, Node.js 10.17.0): Firefox, Node.js 13.11.0
• Operating system and version (desktop or mobile): Windows