The selection indicator should be configurable

[toastersocks]

Situation

Right now the selection indicator is always a checkmark that matches SwiftUI's Picker. It might be nice for this to be configurable.

Solution

There should be a way to configure what the selection indicator is with the current checkmark being default.

Possible approaches

some View

Pass in a ViewBuilder closure to make the selection indicator be whatever we want.

A set of defaults

There could be a default set of selection indicators such as checkmark, bullet, highlight, radioButton, etc...

Combo

We could combine these two approaches with a set of built-in indicators, but also allow a totally custom indicator.

View Modifier vs. init parameter

I would lean more towards a view modifier rather than init parameter for this one.

[toastersocks]

Let's make it a modifier .selectionIndicator that takes a view or view builder