Add "created_at" DateTime to cves.json

[ethicalhack3r]

Hi,

It would be super useful to have a "created_at" DateTime stamp for each entry in the cves.json file.

https://github.com/projectdiscovery/nuclei-templates/blob/main/cves.json

This would make it much easier to determine when a template for a CVE was added, without any additional parsing of the template itself, or Git logs.

Thank you,
Ryan