UIView ~ CGSize operator

I would like to set widthAnchor and heightAnchor directly linking a UIView to a CGSize:
```swift
let iconSize = CGSize(width: 16, height: 16)
viewA ~ iconSize
```
equivalent to
```swift
viewA.widthAnchor.constraint(equalToConstant: iconSize.width).isActive = true
viewA.heightAnchor.constraint(equalToConstant: iconSize.height).isActive = true
```