chore: clean up repo structure and add real schemas

[Anusree-J]

Summary

Restructures the schemas repo around a stable, versioned URL pattern (schemas/<name>/v<version>/schema.json) and replaces placeholder content with real JSON Schemas.

What changed

Cleanup

• Drop the space-in-name energy credentials/ directory
• Move schemas/salary-slip/{schema.json,README.md} → schemas/salary-slip/v1/
• Rename the existing schema.json (which was a sample instance, not a JSON Schema) to example.json and add a real JSON Schema alongside it
• Fix typo (standards|) in root README, list available schemas, document the URL pattern and immutability/versioning policy
• Add CONTRIBUTING.md describing the add/revise workflow

Real schemas added (under schemas/<name>/v1/ with $id matching their raw GitHub URL)

• education, employment, identity, health, business — sourced from OpenCred's bundled built-in templates (packages/schema-engine/src/schemas/); these used to point at https://opencred.dev/schemas/... which is unhosted
• electricity — Customer Credential, sourced from beckn/DEG#208 with upstream attribution in the README

Final tree

schemas/
├── business/v1/{schema.json, README.md}
├── education/v1/{schema.json, README.md}
├── electricity/v1/{schema.json, context.jsonld, example.json, README.md}
├── employment/v1/{schema.json, README.md}
├── health/v1/{schema.json, README.md}
├── identity/v1/{schema.json, README.md}
└── salary-slip/v1/{schema.json, example.json, README.md}

URL pattern

Every schema is reachable at:

https://raw.githubusercontent.com/nfh-trust-labs/opencred-vc-schemas/main/schemas/<name>/v<version>/schema.json

This same URL is the schema's \$id, so JSON Schema processors resolve it directly. OpenCred will reference these URLs in the W3C VC credentialSchema field (follow-up in opencred#300).

Versioning policy

Once v<n> is merged, it is immutable. Breaking and non-breaking shape changes both produce a new v<n+1> directory; older versions stay frozen so existing credentials in the wild keep validating.

Test plan

• All 7 schema.json files parse as valid JSON
• All 5 draft-07 schemas compile cleanly with ajv (with ajv-formats)
• Electricity (draft 2020-12) compiles cleanly with ajv/2020
• schemas/electricity/v1/example.json validates against its schema
• schemas/salary-slip/v1/example.json validates against its schema
• All \$id fields match their raw GitHub URLs

🤖 Generated with Claude Code