Support for Metalua / MoonSharp Lambda Syntax: |x, y| x + y

I'd like to request support for lambda syntax anonymous functions used by [Metalua ](https://github.com/fab13n/metalua)and [MoonSharp](https://github.com/moonsharp-devs/moonsharp).

With lambda syntax

```lua
|x, y| x + y
```

is treated as syntax sugar for:

```lua
function(x, y) return x + y end
```
