DOC-3147: Language code standardization to RFC5646/BCP47 format.

[kemister85]

Ticket: DOC-3147
Parent: TINY-12090

Site: Staging branch

Standardize TinyMCE Language Pack Filenames to RFC5646 Format

Documentation Changes

UI Localization

• modules/ROOT/pages/ui-localization.adoc
  • Added RFC5646 standardization notice
  • Updated examples to use hyphenated format (e.g., 'en-US' instead of 'en_US')

Language Configuration

• modules/ROOT/partials/configuration/language.adoc
  • Updated configuration examples to use RFC5646 format
  • Added note about console warnings for legacy format
  • Updated Swedish example from 'sv_SE' to 'sv-SE'

Spellchecker Documentation

• modules/ROOT/pages/introduction-to-tiny-spellchecker.adoc
  • Added RFC5646 standardization notice
  • Updated all code examples to use hyphenated format

Content Languages Configuration

• modules/ROOT/partials/plugins/spellchecker-content_langs.adoc
  • Updated language codes in content_langs examples

Hunspell Dictionaries

• modules/ROOT/pages/self-hosting-hunspell.adoc
  • Updated file naming conventions to use RFC5646 format
  • Updated flat and nested structure examples
  • Need to verify that the .zip file containing the .aff and .dic file naming convention is not changing @spocke

Custom Dictionaries

• modules/ROOT/pages/custom-dictionaries-for-tiny-spellchecker.adoc
  • Updated file naming patterns to use hyphens
  • Updated examples of dictionary filenames

Language Lists and References

• modules/ROOT/partials/misc/spellchecker-languages.adoc

  • Updated language code table to use RFC5646 format
  • Updated example codes in descriptions

• modules/ROOT/partials/misc/ui-languages.adoc

  • Updated language codes for all supported languages
  • Updated filename examples to use hyphens

Docker Configuration

• modules/ROOT/partials/docker/spelling-service/spelling-service-installation.adoc
  • Updated curl test examples to use RFC5646 format
  • Updated TinyMCE init example
  • Updated log examples to show new format based on incoming changes.

Release Notes

• modules/ROOT/pages/8.0-release-notes.adoc
  • Added comprehensive section on language code standardization
  • Included migration guide with example
  • Added backward compatibility information
  • Added links to relevant documentation sections
  • add link back to migration-guide/breaking changes

Pre-checks:

• Branch prefixed with feature/<version>/, hotfix/<version>/, staging/<version>/, or release/<version>/.
• Included a release note entry for any New product features.
• Validate the above checks with the team.

Review:

• Documentation Team Lead has reviewed