Add harvesting script for ConfIDent conference metadata

[hauschke]

Is your feature request related to a problem? Please describe.
Conference metadata is hard to get. It would be very useful to have a working harvester script for ConfIDent (https://www.confident-conference.org/index.php/Main_Page)

Describe the solution you'd like
A reusable script, maybe based on the JSON fetch.

Describe alternatives you've considered
None, at least not for the VIVO harvester.

Additional context
API overview: https://www.confident-conference.org/index.php/Help:FAQ#How_to_use_the_API