0.31.8

Various fixes & improvements

• MonitorSchedule constructor that validates crontab syntax (#625) by @szokeasaurusrex
• fix(docs): Fix some doc errors that slipped in (#623) by @flub
• docs(tower): Mention how to enable http feature from sentry crate (#622) by @flub
• build(deps): bump rustix from 0.37.23 to 0.37.25 (#619) by @dependabot