[button group] Implement square button group

[manabu-nakamura]

Is your feature request related to a problem? Please describe.
The square button group is not implemented?
https://m3.material.io/components/button-groups/specs#0d2cf762-275c-4693-9484-fe011501439e:

https://github.com/material-components/material-components-android/blob/master/docs/components/ButtonGroup.md

Describe the solution you'd like
Implement the square button group. Add its documentation and example.

Describe alternatives you've considered

<style name="Widget.Material3Expressive.MaterialButtonGroup.Connected.Square">
    <item name="shapeAppearance">@style/ShapeAppearance.M3.Sys.Shape.Corner.Small</item>
</style>