Add new activity flags (#254)

* Add new activity flags

* Add missing commas

src/Discord.Net.Core/Entities/Activities/ActivityProperties.cs

@@ -33,6 +33,18 @@ namespace Discord
         /// <summary>
         ///     Indicates that a user can play this song.
         /// </summary>
-        Play = 0b100000
+        Play = 0b100000,
+        /// <summary>
+        ///     Indicates that a user is playing an activity in a voice channel with friends.
+        /// </summary>
+        PARTY_PRIVACY_FRIENDS = 0b1000000,
+        /// <summary>
+        ///     Indicates that a user is playing an activity in a voice channel.
+        /// </summary>
+        PARTY_PRIVACY_VOICE_CHANNEL = 0b10000000,
+        /// <summary>
+        ///     Indicates that a user is playing an activity in a voice channel.
+        /// </summary>
+        EMBEDDED = 0b10000000
     }
 }