fix: make code compatible with iOS.

Author: jaywcjlove

Package.swift

@@ -6,7 +6,7 @@ import PackageDescription
 let package = Package(
     name: "CodeMirror",
     platforms: [
-        .iOS(.v14),
+        .iOS(.v17),
         .macOS(.v14),
     ],
     products: [

Sources/CodeMirror/CodeMirrorVM.swift

@@ -5,7 +5,13 @@
 //  Created by 王楚江 on 8/11/25.
 //
 
-import AppKit
+#if canImport(AppKit)
+import AppKit   // macOS
+#endif
+
+#if canImport(UIKit)
+import UIKit    // iOS / iPadOS
+#endif
 
 @MainActor
 public class CodeMirrorVM: ObservableObject {