docs: add CLAUDE.md for Claude Code guidance

[LeoFalco]

Summary

Adds a root CLAUDE.md to guide Claude Code (and human contributors) when working in this repo.

This is a docs-companion repository — every script is a self-contained, runnable demo of one Amonamarth API call, not application code — and that shape isn't obvious from a file listing. The guide captures:

• What the repo is: runnable examples for the Amonamarth public REST API; no build and no test runner — scripts self-verify with node:assert, so running a script is its test.
• Commands: nvm use (Node v16), npm install, node <path> to run an example, npm run lint:fix. CI runs super-linter on PRs to master.
• Auth: .env with API_KEY, sent as x-api-key via core/client.js.
• core/ internals: the axios client logs requests/responses, parses XML, and uses validateStatus: () => true (non-2xx doesn't throw); utils.js unwrappers getData / getItems / getFistItem.
• The three-language mirror (pt / en / es) and the rule to keep them in sync, translating only comments and strings.
• The shared script skeleton and StandardJS style every example follows.

Notes

• Docs-only change; no source or dependency changes.
• No PR template exists in this repo.