Make columns shrink equally/make sure they are equal width even on na…

…rrow screens, by giving them a definite width

See https://css-tricks.com/equal-columns-with-flexbox-its-more-complicated-than-you-might-think/#:~:text=If%20everything%20has%20the%20same%20flex-shrink%20%28which%20is,but%20they%20all%20shrink%20at%20the%20same%20rate.

main.sass

@@ -130,6 +130,7 @@ ul
     > *
         flex: 1
         max-height: 100%
+        width: 100px // need a definite width to start with
 
 .scrollParent
     display: flex