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

[janpieper]

It would be cool to use ...> instead of iex> as prompt for multi-line expressions:

Expected

iex> Example.say_hello(
...>   "Belly",
...>   "Peak"
...> )
"Hello Belly Peak!"

Actual

iex> Example.say_hello(
iex>   "Belly",
iex>   "Peak"
iex> )
"Hello Belly Peak!"

[janpieper]

When using ...>, I get a TokenMissingError:

** (TokenMissingError) token missing on example.exs:1:19:
    error: missing terminator: )
    │
  1 │ Example.say_hello(
    │                  │└ missing closing delimiter (expected ")")
    │                  └ unclosed delimiter
    │
    └─ example.exs:1:19