Add plugin stub for notifying GUI language change

PKHeX.Core/Editing/IPlugin.cs

@@ -1,4 +1,4 @@
-namespace PKHeX.Core;
+namespace PKHeX.Core;
 
 /// <summary>
 /// Plugin interface used by an editor to notify third-party code providers.
@@ -26,6 +26,13 @@ public interface IPlugin
     /// </summary>
     void NotifySaveLoaded();
 
+    /// <summary>
+    /// Notifies the plugin that the display language has changed.
+    /// </summary>
+    /// <param name="language">Short code for language name</param>
+    /// <remarks>Useful to translate controls if any added.</remarks>
+    void NotifyDisplayLanguageChanged(string language) { }
+
     /// <summary>
     /// Attempts to load a file using the plugin.
     /// </summary>

PKHeX.WinForms/MainWindow/Main.cs

@@ -974,6 +974,9 @@ public partial class Main : Form
             PKME_Tabs.PopulateFields(pk); // put data back in form
             Text = GetProgramTitle(sav);
         }
+
+        foreach (var plugin in Plugins)
+            plugin.NotifyDisplayLanguageChanged(lang);
     }
     #endregion