Bump dashdash, whitelist shorthand

[Inwerpsel]

Ref: no ticket, just a bump to match the same bump in greenpeace/planet4-plugin-gutenberg-blocks#495

---

This bumps dashdash to the latest version, which supports a shorthand to generate variable names from the selector.

.foo-bar {
  _-- {
    color: green;
    background-color: yellow;
  }
}

produces the same result as

.foo-bar {
  --foo-bar-- {
    color: green;
    background-color: yellow;
  }
}

which is the same as

.foo-bar {
  color: var(--foo-bar--color, green);
  background-color: var(--foo-bar--background-color, yellow);
}

[comzeradd]

Can you adjust also Sonacloud stylelint config if needed?