Consider using font-relative widths and heights in containing elements

[anevins12]

Is your feature request related to a problem? Please describe.
When structural elements contain text, we should consider setting their widths or heights in a way that responds to text size increase (not talking about zoom here).

This came about when looking at the resolution for #15973 . This is fine, but the sidebar is still very cramped with the increase of font size. It could do with being larger.

Describe the solution you'd like
Using em on the container's width or height values so that when text size increases, the containers also increase.

We can start this approach on the sidebar discussed in 15973.

Describe alternatives you've considered
I think can use CSS 'max-width' to define a PX constraint to meet the design, and instead use CSS 'width' as the relative measurement:
.foo { max-width: something-reasonable-px; width: 100em }

[paaljoachim]

@aristath and @ItsJonQ
Is this issue still relevant?

[aristath]

Is this issue still relevant?

I don't think so, all block styles now use em values and not px, with just a few exceptions that don't have anything to do with this ticket.
I'll go ahead and close this issue, if however I am mistaken please feel free to post some clarifications and we can reopen it for further discussion 👍