Fix the schema of the ruby element and fix the logic on permitted-contents

[YusukeHirao]

Fixes #637

What is the purpose of this PR?

• Fix bug
• Fix typo
• Update specs
• Add new rule
• Add new parser
• Improve or refactor rules
• Add a new core feature
• Improve or refactor core features
• Update documents
• Others

Description

Checklist

Fill out the checks for the applicable purpose.

• Fix bug
  • Add the test that can check whether resolved the issue.
• Update specs
  • Element
    • Update global attributes
    • Update content models
    • Add also ARIA that you explored ARIA in HTML Recommendation and Editor's draft
  • Attribute
    • Update global attributes
    • Update IDL attribute
• Add new rule
  • Add a test
  • Add a README document
    • Create an issue that requests translating the doc if you want.
  • Add to index
  • Add JSON schema to schema.json
  • Add to initializer
  • Add to @markuplint/config-presets
• Add new parser
  • Add a test
    • Do a test with some parser.
  • Add to initializer