Consider creating an attestation predicate

[puerco]

The security insights data file captures information about the state of the project at a particular commit that is, essentially, a set of claims about it.

I think the project should consider creating a json variant that can be used as a predicate for an ( @in-toto ) attestation. This would allow us to sign and embed the security insights file (for example in a @sigstore bundle) using the existing tooling from those ecosystems.