Fix numeric SWKB validation (#5627)

* Fix numeric swkbd validation

* GTK

src/Ryujinx.HLE/HOS/Applets/SoftwareKeyboard/NumericCharacterValidation.cs

@@ -0,0 +1,17 @@
+using System.Text.RegularExpressions;
+
+namespace Ryujinx.HLE.HOS.Applets.SoftwareKeyboard
+{
+    public static partial class NumericCharacterValidation
+    {
+        public static bool IsNumeric(char value)
+        {
+            Regex regex = NumericRegex();
+
+            return regex.IsMatch(value.ToString());
+        }
+
+        [GeneratedRegex("[0-9]|.")]
+        private static partial Regex NumericRegex();
+    }
+}