Add LearningResource structured data to curated resources

[LukasWallrich]

Why this needs addressing

Individual curated-resource pages already expose structured front-matter fields such as abstract, material type, education level, primary user, subject area, language, creators, and the external resource URL. However, the live page https://forrt.org/curated_resources/stereotype-threat/ currently exposes BreadcrumbList structured data but no content entity describing the resource.

Requested change

Emit a LearningResource JSON-LD entity from layouts/curated_resources/single.html (or a dedicated partial), populated from existing front matter. Where appropriate include:

• name, url, and abstract;
• learningResourceType, educationalLevel, and audience;
• about, inLanguage, and dateModified;
• verified creators/authors;
• isBasedOn for link_to_resource;
• the FORRT provider/organization.

Use the actual values and omit fields that are absent or ambiguous. Do not claim that generic LearningResource markup guarantees a Google rich result; the goal is accurate machine-readable semantics.

Acceptance criteria

• Representative resource pages emit valid JSON-LD with no empty arrays or placeholder values.
• The structured data matches the visible page content and front matter.
• Existing BreadcrumbList and site-wide Organization data remain valid.
• Validate the output with a JSON parser and a Schema.org validator.

Reference: https://schema.org/LearningResource