Sidebar on smaller screen sets `display: block` instead of the flex

[agatheblues]

There is a bug in bitstyles_phoenix.

It's applying the class u-flex to the sidebar that that will never work for smaller screen. The sidebar's logic to hide and show itself applies an inline style of display: block, which overrides display: flex from .u-flex.

As a result, positioning an element at the bottom of the sidebar for example will not work.