Adds a massban flag to the admin flags (#25327)

Adds a massban flag to the admin flags used on ss14 to ban large amounts of players rom a .tsv file

Co-authored-by: Geekyhobo <66805063+Ahlytlex@users.noreply.github.com>

Content.Shared/Administration/AdminFlags.cs

@@ -89,6 +89,11 @@
         /// </summary>
         EditNotes = 1 << 14,
 
+        /// <summary>
+        ///     Lets you Massban, on SS14.Admin
+        /// </summary>
+        MassBan = 1 << 15,
+
         /// <summary>
         ///     Dangerous host permissions like scsi.
         /// </summary>