docs: fix CommandRegistration doc comment referencing removed CommandData

CommandHook/CommandRegistration.cs

@@ -6,9 +6,9 @@ namespace CommandHook;
 public struct CommandRegistration
 {
     /// <summary>
-    /// Called before the command runs. Set <see cref="CommandData.Cancel"/> on
+    /// Called before the command runs. Return a non-null <see cref="TextCommandResult"/>
-    /// <paramref name="data"/> via the ref parameter inside your delegate to stop
+    /// to cancel the command, report that result to the caller, and skip any
-    /// the command from executing and skip any remaining Before listeners.
+    /// remaining Before listeners. Return null to let the command run.
     /// </summary>
     public readonly CommandBeforeDelegate? Before;