✨ feat: add taxonomy list and single term templates

[welpo]

Summary

This PR adds fallback/default templates for taxonomies other than tags.

Related issue

Resolves #229.

Changes

The changes include the addition of two new fallback templates:

• taxonomy_list.html.
• taxonomy_single.html.

Docs: https://www.getzola.org/documentation/templates/taxonomies/

Useful for users who might need taxonomies other than the default, tags.

The taxonomy terms can be translated if the user adds the necessary lines in their i18n folder. It falls back to the taxonomy name.

Accessibility

Remains teh same as the default tags page(s).

Type of change

• New feature (adds non-breaking functionality)
• Bug fix (fixes an issue without altering 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

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