feat(VSkeletonLoader): add chip-group type

[mixelburg]

Closes #20695

Adds a chip-group type to VSkeletonLoader that renders 4 chip-shaped skeleton bones in a row, mimicking the appearance of a v-chip-group.

Before: Users had to compose their own chip skeletons using type="chip@4" manually.

After: <v-skeleton-loader type="chip-group" /> provides a convenient shorthand.

The new type follows the same pattern as existing composed types like paragraph (text@3) and sentences (text@2).

[J-Sek]

I don't see how it addresses the claim from issue author

It is complicated to make a good looking skeleton loader for a chip group