1. migrate from httpx to curl_cffi
2. CURL: simplified downloads, use ThreadPoolExecutor instead of asyncio
3. exceptions: simplified, use DuckDuckGoSearchException and VQDExtractionException
4. github workflow: added windows and macos
5. tests: removed delays between tests, activated tests for text(backend="lite")
6. CLI: save_json() - set encoding="utf-8" (bugfix for windows)