feat: add dynamic certificate label and icon

[flagrede]

Description

Closes: #2052
Needs: regen-network/regen-sanity#48

• Use credit class label and icon from sanity, if they exist, to display certificate

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How to test

1. with sanity credit class: https://deploy-preview-2166--regen-marketplace.netlify.app/certificate/WyJyZXRpcmVtZW50cyIsMSwxMDAyMTcwNSwwLDBd
2. without sanity credit class: https://deploy-preview-2166--regen-marketplace.netlify.app/certificate/WyJyZXRpcmVtZW50cyIsMSw5ODAyNDM3LDAsMF0=

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[flagrede]

@erikalogie you can test that the certificate is now dynamic here (I've updated the C01 credit class in sanity):

• with sanity credit class (C01): https://deploy-preview-2166--regen-marketplace.netlify.app/certificate/WyJyZXRpcmVtZW50cyIsMSwxMDAyMTcwNSwwLDBd
• without sanity credit class: https://deploy-preview-2166--regen-marketplace.netlify.app/certificate/WyJyZXRpcmVtZW50cyIsMSw5ODAyNDM3LDAsMF0=

[erikalogie]

@flagrede LGTM!

[blushi]

Looks good, just a small nit