New Features
- new callback event: `after_create` ([2842](https://github.com/fastai/fastai/issues/2842))
- This event runs after a `Learner` is constructed. It's useful for initial setup which isn't needed for every `fit`, but just once for each `Learner` (such as setting initial defaults).
- Modified XResNet to support Conv1d / Conv3d ([2744](https://github.com/fastai/fastai/pull/2744)), thanks to [floleuerer](https://github.com/floleuerer)
- Supports different input dimensions, kernel sizes and stride (added parameters ndim, ks, stride). Tested with fastai_audio and fastai time series with promising results.
Bugs Squashed
- `img_size` attribute for `TensorPoint` is not updated properly ([2799](https://github.com/fastai/fastai/pull/2799)), thanks to [IRailean](https://github.com/IRailean)