Add a field for a certificate draft preview link to information provided by the codechecker

When the codechecker publishes the certificate outside of OJS, e.g., on OSF or Zenodo, then they should be able to provide through OJS a preview link to the certificate so that editors (and authors) can inspect it before the certificate goes live.

The field should include some instructions and the links below.

- https://help.zenodo.org/docs/share/link-sharing/
- https://help.osf.io/article/201-create-a-view-only-link-for-a-project
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## Related User Stories

- **C-MM2** (direct): As a codechecker, I want to preview a draft of the CODECHECK certificate...
- C-WB1 (related): As a codechecker, I want a single workbench page in OJS...
- R-SC2 (related): As a reader, I want a direct link from the article's landing page to the CODECHECK certificate's own landing page...

_User story references from the [CHECK-PUB User Stories document](https://codecheck.org.uk/pub/)._