Added checkout calls to the project settings if version control provider is enabled and active.

Author: JimmyDeemo

source/VersionHandlerImpl/src/ProjectSettings.cs

@@ -406,6 +406,13 @@ private static void Save() {
                     return;
                 }
                 Directory.CreateDirectory(Path.GetDirectoryName(PROJECT_SETTINGS_FILE));
+                if (UnityEditor.VersionControl.Provider.enabled && UnityEditor.VersionControl.Provider.isActive) {
+                    var task = UnityEditor.VersionControl.Provider.Checkout(PROJECT_SETTINGS_FILE, 
+                                                                        UnityEditor.VersionControl.CheckoutMode.Exact);
+                    task.Wait();
+                    if (!task.success)
+                        return;
+                }
                 using (var writer = new XmlTextWriter(new StreamWriter(PROJECT_SETTINGS_FILE)) {
                         Formatting = Formatting.Indented,
                     }) {