dockmate

Install command: 
brew install --cask dockmate

Name: Dock Mate

Window previews and controls

https://www.macenhance.com/dockmate

Cask JSON API: /api/cask/dockmate.json

Cask code: dockmate.rb on GitHub

Current version: 0.8.7

Requirements: macOS >= 10.14

Analytics:

Installs (30 days)
dockmate 15
Installs (90 days)
dockmate 38
Installs (365 days)
dockmate 212