Add seed-fetching service

ALttPRandomizer/IdGenerator.cs

@@ -4,7 +4,7 @@
     public class IdGenerator {
         private const string chars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789";
         private const int length = 10;
-        private static Random random = new Random();
+        private static readonly Random random = new Random();
 
         public string GenerateId() {
             var str = new char[length];