Problem Statement
What is a `ViewModifier` in SwiftUI and why would you create a custom one?
Explanation
A `ViewModifier` is a protocol in SwiftUI that you implement to encapsulate a transformation or styling of a view that can be reused. For example you may define a custom modifier for a standard button style. In interviews you may be asked to design or show how you’d structure modifiers for consistent styling in SwiftUI.