Fix typo

flutter/lib/common.dart

@@ -46,7 +46,7 @@ var isWebDesktop = false;
 var version = "";
 int androidVersion = 0;
 
-/// only avaliable for Windows target
+/// only available for Windows target
 int windowsBuildNumber = 0;
 DesktopType? desktopType;
 
@@ -1373,7 +1373,7 @@ Future<Map<String, String>> getHttpHeaders() async {
   };
 }
 
-// Simple wrapper of built-in types for refrence use.
+// Simple wrapper of built-in types for reference use.
 class SimpleWrapper<T> {
   T value;
   SimpleWrapper(this.value);
@@ -1409,7 +1409,7 @@ Future<void> reloadAllWindows() async {
 /// Indicate the flutter app is running in portable mode.
 ///
 /// [Note]
-/// Portable build is only avaliable on Windows.
+/// Portable build is only available on Windows.
 bool isRunningInPortableMode() {
   if (!Platform.isWindows) {
     return false;

flutter/lib/common/widgets/peer_card.dart

@@ -464,7 +464,7 @@ abstract class BasePeerCard extends StatelessWidget {
     );
   }
 
-  /// Only avaliable on Windows.
+  /// Only available on Windows.
   @protected
   MenuEntryBase<String> _createShortCutAction(String id) {
     return MenuEntryButton<String>(

flutter/lib/utils/multi_window_manager.dart

@@ -208,7 +208,7 @@ class RustDeskMultiWindowManager {
 
   /// Remove active window which has [`windowId`]
   /// 
-  /// [Avaliability]
+  /// [Availability]
   /// This function should only be called from main window.
   /// For other windows, please post a unregister(hide) event to main window handler:
   /// `rustDeskWinManager.call(WindowType.Main, kWindowEventHide, {"id": windowId!});`