Add issue creation and editing

ios/Sources/DetailScreens.swift

@@ -87,9 +87,28 @@ final class IssueViewController: MarkdownPageViewController {
 
     override func viewDidLoad() {
         super.viewDidLoad()
+        navigationItem.rightBarButtonItem = UIBarButtonItem(
+            title: "Edit",
+            style: .plain,
+            target: self,
+            action: #selector(editIssue)
+        )
         loadContent(refreshing: false)
     }
 
+    @objc private func editIssue() {
+        let editor = IssueEditorViewController(
+            context: context,
+            owner: owner,
+            repository: repository,
+            number: number
+        ) { [weak self] _ in
+            guard let self else { return }
+            self.dismiss(animated: true) { self.loadContent(refreshing: false) }
+        }
+        present(UINavigationController(rootViewController: editor), animated: true)
+    }
+
     override func loadContent(refreshing: Bool) {
         beginLoading(refreshing: refreshing)
         loadingTask?.cancel()
@@ -538,7 +557,7 @@ final class RepositoryFileViewController: UIViewController, QLPreviewControllerD
     }
 }
 
-private struct RepositoryMarkdownPreview: View {
+struct RepositoryMarkdownPreview: View {
     let source: String
 
     var body: some View {