Is it impossible to pass non copyable Func?

Really dont understand how to pass just function to be executed in scheduler. Without co_awaitable stuff

```cpp
using Task     = fu2::unique_function<void()>;
void submit(Task task) {
    wg_.add(1);
    lf::call([this, task_ = std::move(task)]() mutable {
      task_();
      wg_.done();
    });
  }
```