Duckduckgo-search

1. bugfix in text(backend="lite") - page iteration didn't work,
2. recode text(backend="api") - the payload["s"] parameter is now taken from the page,
3. text() -delays between requests during iteration have been removed,
4. small changes in tests.

The text() function now returns up to 500 unique results.

1. **add async support** (class AsyncDDGS() )
2. add max_results parameter to funstions text(), images(), news(), videos(), maps()
3. improve tests

1) update USERAGENTS,
2) update requirements,
3) small improvements to the code,
4) drop python 3.7, add python 3.12.

1) update USERAGENTS,
2) def _text_api(): update payload,
3) update README.md

1. CLI: download_file - bugfix exceptions,
2. CLI: download_file() - change timeout=10,
3. CLI: _download_results() - change default threads=10,
4. CLI - add proxy parameter to news, videos, answers, suggestions, maps, translate.

1. bugfix in DDGS.text(backend='lite'): removed duplicated results
2. CLI: add `proxy` and `threads` parameters to `ddgs text` and `ddgs images`