Add tooltips for data.gsd.id add reference type

[kurtseifried]

The pull down for reference type lists the various types e.g. WEB, REPORT, FIX, etc. it would be nice to have tooltips popup what each one means. The text from https://ossf.github.io/osv-schema/#references-field would be great:

The known reference type values are:

ADVISORY: A published security advisory for the vulnerability.
ARTICLE: An article or blog post describing the vulnerability.
REPORT: A report, typically on a bug or issue tracker, of the vulnerability.
FIX: A source code browser link to the fix (e.g., a GitHub commit) Note that the fix type is meant for viewing by people using web browsers. Programs interested in analyzing the exact commit range would do better to use the GIT-typed affected[].ranges entries (described above).
PACKAGE: A home web page for the package.
EVIDENCE: A demonstration of the validity of a vulnerability claim, e.g. app.any.run replaying the exploitation of the vulnerability.
WEB: A web page of some unspecified kind.