Add HowTo component for JSON-LD

[garmeeh]

Add HowToJsonLd component following Schema.org HowTo specification for structured data that represents step-by-step instructions.

Features:

• Support for HowToStep, HowToSection, HowToDirection, and HowToTip types
• HowToSupply and HowToTool for materials and equipment
• Duration properties (prepTime, performTime, totalTime) in ISO 8601 format
• estimatedCost as string or MonetaryAmount object
• yield as string or QuantitativeValue
• Flexible @type handling - developers don't need to specify @type
• Video support via VideoObject
• ImageObject support for steps and materials

Includes:

• Type definitions in src/types/howto.types.ts
• Processing functions in src/utils/processors.ts
• Unit tests with comprehensive coverage
• E2E tests for basic and advanced usage
• Example pages in the app-router-showcase
• Documentation in README.md

[github-actions]

📝 Changeset Required

This PR includes code changes but is missing a changeset. Changesets help us:

• Track changes for release notes
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? Summary › Fixed TypeScript types for ArticleJsonLd component

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