Add screenshot features for linux and win32#266

Draft

Beanow wants to merge 4 commits intotauri-apps:devfrom Beanow:experiment/screenshot

+256-15

Commits on May 16, 2021

Add screenshot features for linux and win32
Beanow
committed

Commits on May 28, 2021

Merge branch 'dev' into experiment/screenshot
Yu-Wei Wu
committed
Add snapshot handler on mac
Yu-Wei Wu
committed
Pass NSImage as vector to handler
Yu-Wei Wu
committed