bug#62536: 30.0.50; Can we add """ ... """ electric pair in elixir, just like python

[Mou Tong]

> Will it make sense to also add a newline when closing a multiline
> comment/heredoc? It feels smoother to me rather than having to press
> enter and then C-o ( open-line ) to position the cursor correctly?

I agree with you, but I think it might be better to imitate what
`c-mode` did:

```c
int main () {|}
```

When `electric-pair-mode` is on, input the left `{`, Emacs helps you
complete the right `}`. After press enter, your cursor will move to the
next line and auto-indented according to your offset config:

```c
int main () {
  |
}
```

So how about making it work like this?

```elixir-ts
@doc """|"""

# after press enter
@doc """
  |
"""
```