WordAds Block: Include Hide from Desktop Option

#### Is your feature request related to a problem? Please describe.
The Ad block has an option to hide the block on mobile devices, but not an option to hide the Ad block on larger screens -- this prevents being able to set up a large Leaderboard ad that appears on desktops, and a different size ad to be shown only for mobile

#### Describe the solution you'd like
Add a toggle to hide an Ad block on larger displays, or provide additional Ad block display options

#### Describe alternatives you've considered
None that I can think of that wouldn't require CSS, which would cause other issues

#### Additional context
[](https://d.pr/i/IkDwfK/YhLZJJVFE8)

Requested in 3593524-zen

The issue names no files, tests, or entry points, so first locate the WordAds block implementation and its existing mobile-visibility option. Confirm how block display settings are represented, then verify that a desktop-only toggle can coexist with the mobile option and produces the requested separate desktop and mobile ad behavior.

Written by the indexing model from the issue text.