Added a package for Screencloud, a program for taking screenshots and
uploading them to various websites.
This package was a bit finicky due to some nonsense in the CMakeLists
file, but it seems to work properly.
The package also includes API keys for the screencloud.net website.
According to the author of the Arch Linux User Repo package for
screencloud, these keys are only used for usage tracking, so we should
be fine including them in the package here.
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