docs(CommandRegistration): add XML doc comments to Before/After fields and constructor

CommandHook/CommandRegistration.cs

@@ -1,10 +1,26 @@
 namespace CommandHook;
 
+/// <summary>
+/// The pair of callbacks a listener provides for a command. Either one can be null.
+/// </summary>
 public struct CommandRegistration
 {
+    /// <summary>
+    /// Called before the command runs. Set <see cref="CommandData.Cancel"/> on
+    /// <paramref name="data"/> via the ref parameter inside your delegate to stop
+    /// the command from executing and skip any remaining Before listeners.
+    /// </summary>
     public readonly CommandBeforeDelegate? Before;
+
+    /// <summary>
+    /// Called after the command runs, with its result. Not called if a Before
+    /// listener cancelled the command.
+    /// </summary>
     public readonly CommandAfterDelegate? After;
 
+    /// <summary>
+    /// Creates a registration. Pass null for either delegate to only hook one side.
+    /// </summary>
     public CommandRegistration(CommandBeforeDelegate? before, CommandAfterDelegate? after)
     {
         Before = before;