Fix Modifier ValueStr

Elwig/Helpers/Utils.cs

@@ -9,6 +9,7 @@ using System.IO.Ports;
 using System.Net.Sockets;
 using Elwig.Dialogs;
 using System.Text;
+using System.Numerics;
 
 namespace Elwig.Helpers {
     public static partial class Utils {
@@ -234,5 +235,12 @@ namespace Elwig.Helpers {
                 return Text;
             }
         }
+
+        public static string GetSign<T>(T number) where T : INumber<T>
+            => T.Sign(number) switch {
+                < 0 => "\u2212",  // minus
+                  0 => "\u00b1",  // plus minus
+                > 0 => "+",
+            };
     }
 }