glvd: Consider using EUVD as an input source

[fwilhe]

EUVD might be an alternative to CVE and NVD.
This alternative might be needed if the CVE or NVD program becomes unreliable in the future.
An EU-based program would make sense given our work with the NeoNephos foundation.

API Docs: https://euvd.enisa.europa.eu/apidoc

Adding another input source might be feasible, but the DB schema of glvd is heavily based on CVE IDs as keys, so this would have to be reworked.