docs: add api-call-examples with tested Wikibase REST API examples
The examples demonstrate how to:
- Create an author item with label, description, and key statements (P31, P21, P106).
- Create a work item with properties (P31, P7937).
- Add a new statement (P27: Uruguay).
- Modify an existing statement to change the value (P27: Bolivia).
- Outreachy Task: T405635
OUTPUTS:


