feat(transloco): 🎸 auto-detect public folder in ng-add

[shaharkazaz]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/jsverse/transloco/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

The ng-add schematic hardcodes the translation files path to assets/i18n/, which doesn't work properly with Angular 18+ projects that use the new public/ folder structure instead of src/assets/.

Issue Number: #818

What is the new behavior?

The ng-add schematic now automatically detects whether to use public/i18n/ or assets/i18n/ based on:

1. Folder detection: Checks if /public or ${sourceRoot}/assets exists
2. Version detection: Falls back to checking Angular version in package.json (18+ uses public/)
3. User override: Respects explicit --path parameter if provided

This ensures translation files are placed in the correct location and the HTTP loader uses the right URL path for both modern and legacy Angular projects.

Does this PR introduce a breaking change?

• Yes
• No

Other information

The implementation maintains full backward compatibility while adding intelligent detection for Angular 18+ projects. All existing projects continue to work as before, while new Angular 18+ projects automatically get the correct public/ folder configuration.

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commit: 82ee48d

[shaharkazaz]

Verified on an Angular v16 and v18 project.