Render screenshots

[koppor]

https://apidia.net/mvn/org.controlsfx/controlsfx/11.2.2/?pck=org.controlsfx.control&cls=.ToggleSwitch

https://javadoc.io/doc/org.controlsfx/controlsfx/8.40.13/org/controlsfx/control/ToggleSwitch.html

[Stewori]

For now, I quickly fixed this for controlsfx. The issue is that the default policy is to generate docs from content of the maven central source distribution. If the image files are in the sources, they are also in the APIdia docs. Getting resources from github repos is a can of worms, but an intermediate solution can be to extract image files from the javadoc distribution. However, getting and checking the javadoc distribution every time would be expensive, while images occur only in a small minority of project docs. So, this has to be adaptively - check for dead links to images and check javadoc distribution only if needed. That's doable, but a bigger effort, so won't be fixed generally in short term.