docs: add contribution and contributor information

[DannyvdSluijs]

Fixes #391

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

SECURITY.md:13

• [nitpick] This sentence could be clearer. Suggestion: 'JSON Schema uses the GitHub feature to safely report vulnerabilities. Please report them using https://github.com/jsonrainbow/json-schema/security.'

JSON Schema uses the GitHub feature to safely report vulnerabilities, please report them using https://github.com/jsonrainbow/json-schema/security