Visual glitch in non-rounded dark dialog

[srknzl]

Describe the bug
Visual glitch in dark dialogs (not rounded ones)

To Reproduce

Steps to reproduce the behavior:

1. Go to https://nostalgic-css.github.io/NES.css/
2. Click on "open dark dialog"
3. See glitch

Expected behavior

Screenshots

how it is right now:

what it should look like:

Environment:

• OS: Ubuntu 20.04
• Browser: Chrome Version 89.0.4389.90 (Official Build) (64-bit)
• Build environment (i.e. NodeJS): None

Suggestion(s) for fixing this issue
This css block causes this glitch, I don't know what it does.

https://github.com/nostalgic-css/NES.css/blob/master/scss/elements/dialogs.scss#L26

Disabling "position: absolute" in dev tools fixes the glitch

Additional context

[yslius]

I think the aim was to make it similar to Container.is-dark.

scss\elements\containers.scss

&::after {
  position: absolute;
  top: -$border-size * 1.8;
  right: -$border-size * 1.8;
  bottom: -$border-size * 1.8;
  left: -$border-size * 1.8;
  z-index: -1;
  content: "";
  background-color: $base-color;
}

But, since it is difficult to realize on the dialog, I think that absolute is not necessary.
I sent a pull request for this matter.
#474