[commands] Add withDeadline modifier (#7299)

Co-authored-by: Ryan Blue <ryanzblue@gmail.com>

wpilibNewCommands/src/main/native/include/frc2/command/CommandPtr.h

@@ -182,6 +182,16 @@ class CommandPtr final {
   [[nodiscard]]
   CommandPtr OnlyIf(std::function<bool()> condition) &&;
 
+  /**
+   * Creates a new command that runs this command and the deadline in parallel,
+   * finishing (and interrupting this command) when the deadline finishes.
+   *
+   * @param deadline the deadline of the command group
+   * @return the decorated command
+   * @see DeadlineFor
+   */
+  CommandPtr WithDeadline(CommandPtr&& deadline) &&;
+
   /**
    * Decorates this command with a set of commands to run parallel to it, ending
    * when the calling command ends and interrupting all the others. Often more