Fix CSS issue by changing webkit-box to flex

Since the webpack change there's certain cases where the post list summary text bleeds outside the div, and it was caused by the css loaders not showing -webkit-box-flex property, which is deprecated. Changed webkit-box display to flex (The new flexbox as documented https://css-tricks.com/old-flexbox-and-new-flexbox/ )

merged

mentioned in commit 17a63a10

mentioned in commit wallet@9e229f1c