docs: add list_repo_pulls to readme

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Co-Authored-By: Claude Opus 4.5 <[e-mail]>

README.md

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 - `create_repo_issue(repo, title, body, labels)` - create an issue with optional labels
 - `update_repo_issue(repo, issue_id, title, body, labels)` - update an issue's title, body, and/or labels
 - `delete_repo_issue(repo, issue_id)` - delete an issue
-- `list_repo_issues(repo, limit, cursor)` - list issues for a repository
+- `list_repo_issues(repo, limit)` - list issues for a repository
 - `list_repo_labels(repo)` - list available labels for a repository
+
+### pull requests
+- `list_repo_pulls(repo, limit)` - list PRs targeting a repository (only shows PRs you created)
 
 ## development