Add API documentation for set_original_claim

[jayjay-w]

Description

Add API documentation for set_original_claim in the createProjectMedia mutation.

References: CV2-4676

How has this been tested?

Confirmed that the changes are well formatted and the query example works.

Checklist

• I have performed a self-review of my own code
• I have added unit and feature tests, if the PR implements a new feature or otherwise would benefit from additional testing
• I have added regression tests, if the PR fixes a bug
• I have added logging, exception reporting, and custom tracing with any additional information required for debugging
• I considered secure coding practices when writing this code. Any security concerns are noted above.
• I have commented my code in hard-to-understand areas, if any
• I have made needed changes to the README
• My changes generate no new warnings
• If I added a third party module, I included a rationale for doing so and followed our current guidelines

[caiosba]

Thanks @jayjay-w , and please remember to update the documentation here too: https://github.com/meedan/check/wiki/GraphQL-query-examples#create-fact-check

[vasconsaurus]

I have a tiny nitpick/suggestion, feel free to ignore it.
I would change line 272 so that the heading is in the same hierarchy as the Create medias (

check-api/doc/api-user.md

Line 272 in 8bbfb88

### Create original claim when creating media

)

## Create media with original claim

—
Seemingly unrelated to this PR, but in this link: https://github.com/meedan/check/wiki/GraphQL-query-examples#create-fact-check

I would move Create original claim when creating fact check to the Create fact-check section. And add it as a last item there, Create a fact-check with an original claim, instead of leaving it under Update a fact-check.

[jayjay-w]

@vasconsaurus this is ready for your re-review.

---

Regarding, https://github.com/meedan/check/wiki/GraphQL-query-examples#create-original-claim-when-creating-fact-check, I updated it directly and now it should be in the correct section.

[vasconsaurus]

Thanks @jayjay-w! Looks great 🚀

[caiosba]

@jayjay-w we need this in develop (no need to revert the merge to master though)