AlternationPatternNode

Create a new node that replaces the usage of `Binary` within pattern matching expressions to represent the use of the `|` operator.

For example:

```ruby
case foo
in Bar | Baz
end
```

In the above expression `Bar | Baz` is set as a `Binary` in Syntax Tree. Instead, we should have our own node for it.

YARP has: `left`, `right`, `operator_loc`, and `location` on it.