Added new bulk challenge OAuth scope (#519)

Author: tanczosm

src/AspNet.Security.OAuth.Lichess/LichessAuthenticationConstants.cs

@@ -42,6 +42,11 @@ public static class Scopes
             /// </summary>
             public const string ChallengeWrite = "challenge:write";
 
+            /// <summary>
+            /// Create or delete bulk challenges
+            /// </summary>
+            public const string ChallengeBulk = "challenge:bulk";
+
             /// <summary>
             /// Read private studies and broadcasts
             /// </summary>