shiny/screen: new package.

Change-Id: Ib0a6296b9c117d64fc76fc6abe59ccb7da3bbae1
Reviewed-on: https://go-review.googlesource.com/12568
Reviewed-by: Rob Pike <r@golang.org>
tree: 4b825dc642cb6eb9a060e54bf8d69288fbee4904

This tree is empty.