Remove default style class from SpeedkitImage & SpeedkitPicture

[woolimi]

Describe the bug
Hello!
I was trying to migrate nuxt-img component to SpeedkitImage, and then realized that legacy styles are all broken.
That's caused by the own style of SpeedkitImage like below

<style lang="postcss" scoped>
/*! purgecss start ignore */
.nuxt-speedkit-image {
  content-visibility: auto;
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}
/*! purgecss end ignore */
</style>

However, I think this class should be removed and let user decide style.

Expected behavior

Remove default style and let user customize styling on their own.

[Triloworld]

Propose to add:
Option: defaultCss
By default true and can be disabled - to easily update in minor version without breaking existing stuff
Change to false to have components without any: styles or css files
Will be nice and sufficient to remove that code.

Better solution is to have major version without styles that is better aligned to any design guid lines :) Easily and nicely without overhead