Add a variant to Blankstate that makes it easier to use in small areas

[mperrotti]

This change is based on the patterns documented in #548

Currently, our Blankslate component only works well to replace larger regions of content. It feels way too large when used in smaller spaces such as in the SelectPanel body.

Examples

Current Blankslate

A smaller Blankslate variant

We want to support something like this.

[mperrotti]

Filed in wrong repo