Search Douyin (all types) V3

Returns Douyin general search results (V3), returning mixed cards: videos, users, related words, etc. Optional inputs: page, offset, keyword, backtrace, search_id. For pagination, pass back offset, search_id and backtrace from data.pagination of the previous response, and increment page by 1. For the first request set offset to 0, page to 1, and search_id / backtrace to empty strings.