feat: add BasePower abstraction

Players/PlayerValidations/IsValid.cs

@@ -0,0 +1,20 @@
+using CounterStrikeSharp.API.Core;
+
+namespace Cs2SuperPowers.Players.PlayerValidations;
+
+public class IsValid : IValidation<CCSPlayerController>
+{
+    public bool Validate(CCSPlayerController? player)
+    {
+        return player?.IsValid == true;
+    }
+}
+
+public static class IsValidExtensions
+{
+    public static ValidationBuilder<CCSPlayerController> IsValid(this ValidationBuilder<CCSPlayerController> builder)
+    {
+        builder.Add(new IsValid());
+        return builder;
+    }
+}