CI: warn if a shared SVG was modified

[KjellMorgenstern]

Each time a change is submitted to the fritzing-part repo, we run a set of scripts to check the parts.

Not all know automated checks are yet integrated. One additional check might be:

• warn if a shared SVG is edited : In general, a copy of the SVG should be used. If the change was really intended to affect multiple parts, the warning can be ignored.