use GridCells.Adaptive()

[joreilly]

Not that important in context of what's being demonstrated in sample but just capturing in PR in case useful. It's cool as well that GridCells.Adaptive() works across platforms (screenshot here is from iPhone simulator)

btw branch name here is misleading as originally thought I'd have to use https://github.com/chrisbanes/material3-windowsizeclass-multiplatform

I also changed button height here so it looked ok in phone landscape mode but maybe better way to do that.