Summary

• Add an EngineName union for documented SerpApi engine names.
• Replace the previous unbounded EngineParameters = Record<string, any> surface with a minimal typed layer for core search parameters, while still allowing engine-specific query parameters that are not modeled yet.
• Type the getJson and getHtml overloads so both object-form and legacy engine-first calls validate engine names.
• Add TypeScript compile coverage and a README TypeScript example.

This is intentionally not a full engine-specific schema pass. It creates a lowest-level verifiable TypeScript foundation first: engine names and common Search API parameters are typed, while per-engine parameter schemas can be added incrementally later.

Validation

• deno fmt --check
• deno check tests/types_test.ts
• deno task test
• deno task npm
• git diff --check

Note: deno lint currently fails on the existing inline https://deno.land/... imports under Deno 2's no-import-prefix rule, so this PR leaves lint configuration unchanged.

Fixes #33