Add opam manifest

[xoriath]

Add manifest of the opam cli from https://github.com/ocaml/opam

Closes #14217

• [x] I have read the Contributing Guide.

[xoriath]

/verify

[github-actions[bot]]

Your changes do not pass checks.

opam

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [ ] Autoupdate

[github-actions[bot]]

Your changes do not pass checks.

opam

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [ ] Autoupdate

[xoriath]

/verify

[github-actions[bot]]

All changes look good.

Wait for review from human collaborators.

opam

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [x] Autoupdate

[aliesbelik]

Duplicates PR already created in Main bucket: ScoopInstaller/Main#6196.

[xoriath]

Argh, I didn't find a Issue for opam in the main bucket and assumed there wouldn't be a PR for it :)