Promo Card and Event Card image thumbnail cropping

Problem/Motivation

Cards currently allow a height and width to be defined in styles, however they only support 2 breakpoint changes. In all the sizes in-between, the image fills the top region of the card and can lead to cropping either above and below, on the side, or both. This makes it hard for images to be provided by the content editor, as no image correctly sits in that available space.

By changing image to lock their aspect ratio, the full image will always appear the same at all breakpoints. This also means that the image height will shrink as cards change width.