New Features
- Allow attrs to be added to `FT` using `__call__` ([591](https://github.com/fastai/fastcore/issues/591))
- Experimental support for `FT.__call__`, h/t cgarciae ([590](https://github.com/fastai/fastcore/issues/590))
- `FT` interoperability with Django and Jinja using `__html__()` protocol ([589](https://github.com/fastai/fastcore/pull/589)), thanks to [collinanderson](https://github.com/collinanderson)