feat(issue): add body field to IssueItem type and implement issue creation and completion routes

- Added 'body' field to IssueItem type in index.ts
- Created new routes for issue creation and completion in issue.ts
- Implemented validation for required parameters in issue creation and completion
- Added a new list route for issues in list.ts

src/issue/index.ts

@@ -26,6 +26,7 @@ export type IssueItem = {
   author: IssueAuthor;
   labels: IssueLabel[];
 
+  body: string;
   last_acted_at: string;
   number: string;
   priority: string;