SPRINGFIELD — A proposal in the Illinois Senate would set requirements for minimum women’s representation on Illinois-based corporations’ boards.Senate Bill 76 would mandates how many women must be on boards of publicly held domestic and foreign corporations whose principal executive offices are located in the state. Sponsored by Democratic Sen. Cristina Castro of Elgin, the bill would require at least one woman to be on each corporate board by the summer of 2020. And by the end of 2022, the proposal …