Upgrade stylelint to v16

### Description

In the `@alleyinteractive/stylelint-config` package, bump the version of `stylelint` we are using to v16 (the latest as of this writing) for better compatibility with current versions of stylelint-related tools.

### Use Case

When I install `@alleyinteractive/stylelint-config` it should be compatible with the latest version of stylelint.