Proposal: Create a minimum aspect ratio for hero images

[Pinpickle]

Currently, hero images are a fixed width, and their "foreground" will expand to fit the space without clipping them.

Some hero foregrounds (see Git) have images that are expected to fill the full height of the image. Once the hero image gets thin enough, that would in fact be violated.

As this extra height isn't really adding anything, I'm proposing we have a minimum aspect ratio for hero images (e.g. 16:9), and if maintaining constant height would make it thinner than that ratio, the height is decreased (this can be done with CSS).

[Pinpickle]

I should have been clearer about the downsides of this approach, so I'm not sure if we should actually do this. The biggest downside is that we can't have thin and tall heroes (even square ones). Which is a nice property, especially for the home page where we put a hero next to something.