Darken Bases card covers in dark mode

[greetclammy]

Is your feature request related to a problem? Please describe.
I really like how the theme darkens images in dark mode. I noticed that Bases card covers are exempt from this though.

Describe the solution you'd like
Title.

---

I made it work with:

.theme-dark .bases-cards-cover {
  opacity: 0.7 !important;
  transition: opacity .25s linear;
}

.theme-dark .bases-cards-cover:hover {
  opacity: 1 !important;
}