This commit `smart` as a new and default anchor in `Fill`.
So:
```html
{{ $image.Fill "200x200" }}
```
Is, with default configuration, the same as:
```html
{{ $image.Fill "200x200" "smart" }}
```
You can change this default in your `config.toml`:
```toml
[imaging]
[imaging]
resampleFilter = "box"
quality = 68
anchor = "Smart"
```
Fixes#4375
