The controversial proposal from the U.K.'s Green Party would be separate from sick leave or vacation daysWoman suffering period crampsCredit: Moyo Studio / Getty ImagesNEED TO KNOWDetails have leaked about a controversial proposal from U.K.'s Green Party, which would allow 3 days off a month for menstrual leaveSupporters say the policy could reduce stigma and economic costs tied to absenteeism from painful menstrual conditionsCritics argue the p…