[commands] Add static Trigger factories for robot mode changes (#5902)

wpilibNewCommands/src/main/native/include/frc2/command/button/Trigger.h

@@ -268,6 +268,12 @@ class Trigger {
                    frc::Debouncer::DebounceType type =
                        frc::Debouncer::DebounceType::kRising);
 
+  /**
+   * Returns the current state of this trigger.
+   * @return A bool representing the current state of the trigger.
+   */
+  bool Get() const;
+
  private:
   frc::EventLoop* m_loop;
   std::function<bool()> m_condition;