add Utils class and Utils.ReadLineSecure()

Utils.cs

@@ -0,0 +1,46 @@
+using System;
+
+namespace SteamGuard
+{
+	public static class Utils
+	{
+		public static string ReadLineSecure()
+		{
+			string text = "";
+			ConsoleKeyInfo key;
+			int cursorIndex = 0;
+			do
+			{
+				key = Console.ReadKey(true);
+				if ((int)key.Key >= 65 && (int)key.Key <= 90)
+				{
+					text.Insert(cursorIndex, key.KeyChar.ToString());
+					cursorIndex++;
+				}
+				else if (key.Key == ConsoleKey.Backspace && cursorIndex > 0)
+				{
+					text.Remove(cursorIndex - 1, 1);
+					cursorIndex--;
+				}
+				else if (key.Key == ConsoleKey.RightArrow)
+				{
+					cursorIndex++;
+				}
+				else if (key.Key == ConsoleKey.LeftArrow)
+				{
+					cursorIndex--;
+				}
+
+				if (cursorIndex < 0)
+				{
+					cursorIndex = 0;
+				}
+				else if (cursorIndex > text.Length)
+				{
+					cursorIndex = text.Length - 1;
+				}
+			} while (key.Key != ConsoleKey.Enter);
+			return text;
+		}
+	}
+}