Core - Fix plugins without a version in their plugin.json always being considered incompatible

src/Artemis.Core/Plugins/PluginInfo.cs

@@ -10,7 +10,7 @@ namespace Artemis.Core;
 /// </summary>
 public class PluginInfo : CorePropertyChanged, IPrerequisitesSubject
 {
-    private Version? _api;
+    private Version? _api = new(1, 0, 0);
     private string? _author;
     private bool _autoEnableFeatures = true;
     private string? _description;