Using conformance suite to build supported features matrix

[haydentherapper]

Description

I would like to use the conformance suite to build a matrix of supported features per client. This can be used by users who want to verify which client they should leverage based on their requirements. This can also be used when deciding if a client is ready for a 1.0 release.

This can be implemented by monitoring what tests are skipped or marked as xfail since failure is expected due to a feature not being implemented. One way I was thinking this could be implemented is a job that monitors instances of the reusable workflow across the Sigstore org.