Extract data from `.bindl-lock.yaml`

[wilsonehusin]

I would like a command (e.g. bindl export) to extract data available in .bindl-lock.yaml to a file or STDOUT. This would help users to independently verify signatures that we store in .bindl-lock.yaml.

Roughly speaking, how do we make it easy to do a workflow like (not verbatim) the following:

❯ bindl get goreleaser
❯ bindl export goreleaser.cosign[0].artifact > goreleaser-checksums.txt
❯ bindl export goreleaser.cosign[0].certificate > goreleaser-checksums.txt.pem
❯ bindl export goreleaser.cosign[0].signature > goreleaser-checksums.txt.sig
❯ cosign verify-blob goreleaser-checksums.txt \
    --signature goreleaser-checksums.txt.sig \
    --cert goreleaser-checksums.txt.pem