Method joinable

libs/base/thread.hpp:102–102

  id get_id() const noexcept { return m_thread.get_id(); }
  void join() { m_thread.join(); }
  bool joinable() const noexcept { return m_thread.joinable(); }
  native_handle_type native_handle() { return m_thread.native_handle(); }
  void swap(SimpleThread & x) noexcept { m_thread.swap(x.m_thread); }