feat: Add Serialize to all data structures

update version to 4.1.0

make FinancialEvent visible

Update async_impl.rs, blocking_impl.rs, lib.rs, and 2 more files

small fix for debug mode

fix: improve "too many requests" error detection

remove pub

removed comments

added handling of 429 error: YahooError::TooManyRequests

fix readme and doc tests

update readme

apply fmt and clippy

update version to 4.0.0

remove search for options since it is discontinued

update dependencies