cosign v1.12.1 released

[Carlos Tadeu Panato Jr]

Hello Sigstore Community

cosign v1.12.1 release: https://github.com/sigstore/cosign/releases/tag/v1.12.1

Please note:

Pulls Fulcio root and intermediate when `--certificate-chain` is not passed into `verify-blob` command. The v1.12.0 release introduced a regression: when `COSIGN_EXPERIMENTAL` was not set, cosign `verify-blob` would check a ` --certificate` (without a `--certificate-chain` provided) against the operating system root CA bundle. In this release, Cosign checks the certificate against Fulcio's CA root instead (restoring the earlier behavior).

Thanks