Code blocks not full width on mobile

[stephanlachnit]

The problem in a nutshell:

The culprit is assets/scss/shortcodes/cards-pane.scss. The file hard-codes a max-width, which works on a desktop-like layout, but not on mobile. I think the correct fix is to change the linked lines to

.card-deck {
	@extend .td-max-width-on-larger-screens;
}
.card {
    @extend .td-max-width-on-larger-screens;

It looks correct on most things, but I haven't tried this with all possible card-pane configs so I'm not entirely sure. Please let me know if I should open a PR.

[LisaFC]

Yes, please do open a PR, thanks for spotting this problem! @deining can you comment/review?