CSS3 Three Equal Flex Column
RJM Programming - December, 2021 ... thanks to
https://www.tutorialrepublic.com/css-tutorial/css3-flexible-box-layouts.php
Item 1
Cell 1
Cell 2
Cell 3
Cell 4
Item 2
Cell 1
Cell 2
Cell 3
Cell 4
Item 3
Cell 1
Cell 2
Cell 3
Cell 4