Added a password rule engine

Bitvault/SpecialCharRule.cs

@@ -0,0 +1,12 @@
+using System.Text.RegularExpressions;
+
+namespace Bitvault;
+
+public partial class SpecialCharRule : IPasswordRule
+{
+    public int CalculateScore(string password) => 
+        Regex().IsMatch(password) ? 2 : 0;
+
+    [GeneratedRegex(@"[^a-zA-Z0-9]")]
+    private static partial Regex Regex();
+}