Flameshot: [Feature] Support scroll screenshot

[ZetaoYang]

The scrolling screenshot interaction of this Mac application Xnip is worth learning, I think flameshot can also be achieved.

the gif(compressed) animation:

[lupoDharkael]

I don't think this will be implemented as Flameshot works with static images.
This approach makes portability way easier for multiple desktops (compositors) and operating systems.

I would be nice to have something like this but it doesn't fit in the actual design of the project.