Now we have a CODEOWNERS file a reviewer is assigned automatically,
so there's no need for this.
It also misfires a bunch (maybe if there are no _pending_ reviewers
because they've already reviewed?), so removing it fixes that noise.
Make danger check view changes
Add a check that if a file with @Preview or @LargeHeightPreview
in it is changed, then the corresponding build file includes
the showkase processor.
Also change the check that prompts about screenshots to use
the same @Preview logic instead of checking for "/layout" in
the path which doesn't work with compose.
Also add missing showkase processors
Chris Smith