add yandex() `use_cache` deletes if_none(a,b), because b will be computed first, so fix if ... else ... update README.md
4.6.20
make tencent(),deepl() stronger with language_map. make youdao() stronger with `action` and `lts`. speed request with `use_cache`. add type hints for function. `use_domain` --> `professional_field`
4.6.18
make youdao('sentences length more than 50','errCode40') stronger.
4.6.10
make google('emoji') stronger. make requests of server region stronger.
4.6.0
update README.md translator & translate-api upgrade version synchronously.