[Feature] Add support for trading pair NuCypher (NU)

Author: dougdellolio

Diff for: CoinbasePro/Shared/Types/Currency.cs

@@ -44,6 +44,7 @@ public enum Currency
         BAL,
         REN,
         CGLD,
-        WBTC
+        WBTC,
+        NU
     }
 }

Diff for: CoinbasePro/Shared/Types/ProductType.cs

@@ -203,6 +203,14 @@ public enum ProductType
         [EnumMember(Value = "WBTC-BTC")]
         WbtcBtc,
         [EnumMember(Value = "WBTC-USD")]
-        WbtcUsd
+        WbtcUsd,
+        [EnumMember(Value = "NU-USD")]
+        NuUsd,
+        [EnumMember(Value = "NU-EUR")]
+        NuEur,
+        [EnumMember(Value = "NU-GBP")]
+        NuGbp,
+        [EnumMember(Value = "NU-BTC")]
+        NuBtc
     }
 }