✨ feat: add option to show author in post metadata

[welpo]

Summary

Adds show_author configuration option. This will display the authors set on authors = [] in the front matter of the post. If this is not available, it will fall back to author = ""in config.toml.

Related issue

Resolves #319.

Changes

• update page.html to render the author(s) in the metadata
• i18n files updated with new strings to list authors
• format_date.html updated to ensure consistent spacing

Accessibility

Uses semantic HTML.

Screenshots

Type of change

• [ ] Bug fix (fixes an issue without altering functionality)
• [X] New feature (adds non-breaking functionality)
• [ ] Breaking change (alters existing functionality)
• [ ] UI/UX improvement (enhances user interface without altering functionality)
• [ ] Refactor (improves code quality without altering functionality)
• [ ] Documentation update
• [ ] Other (please describe below)

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Checklist

• [X] I have verified the accessibility of my changes
• [X] I have tested all possible scenarios for this change
• [X] I have updated theme.toml with a sane default for the feature
• [X] I have made corresponding changes to the documentation:
  • [X] Updated config.toml comments
  • [X] Updated theme.toml comments
  • [X] Updated "Mastering tabi" post in English
  • [X] (Optional) Updated "Mastering tabi" post in Spanish
  • [X] (Optional) Updated "Mastering tabi" post in Catalan