Use `...>` for multi-line expressions

It would be cool to use `...>` instead of `iex>` as prompt for multi-line expressions:

## Expected

```elixir
iex> Example.say_hello(
...>   "Belly",
...>   "Peak"
...> )
"Hello Belly Peak!"
```

## Actual

```elixir
iex> Example.say_hello(
iex>   "Belly",
iex>   "Peak"
iex> )
"Hello Belly Peak!"
```