Consider providing a template for record feedback

[andrewpollock]

We're seeking to shorten the feedback loop by directly connecting OSV.dev downstream consumers of Python Advisory Database vulnerabilities with the Python Advisory Database for any corrective feedback on individual records.

We can direct link users to https://github.com/psf/advisory-database/issues/new, but a blank issue page with no explicit call to action is going to be a less successful user journey than something like what we have with https://github.com/google/osv.dev/issues/new?template=converted-nvd-cve-data-quality-report.md

See google/osv.dev#2191 for more context.

[MANAS225]

OSV.dev directs users to this repository to report problems in advisory
records, but they currently land on a blank issue page.

I would like to add a structured GitHub issue template to guide users in
reporting advisory data quality problems (incorrect affected versions,
missing backports, wrong commits, etc.).

This would improve the feedback loop mentioned in google/osv.dev#2191.

I’d be happy to work on this if it sounds acceptable.