Material UI v5: rename Skeleton's variants

Proprietary

Renames circle to circular and rect to rectangular, and their classes. Ported from the MUI codemod v5.0.0/skeleton-variant.

org.openrewrite.react.mui.v5.skeleton-variant
mod run . --recipe=org.openrewrite.react.mui.v5.skeleton-variant

Install it once from Recipe actions, then run it on every repository under the current directory. New to the Moderne CLI? Set it up.