New attribute syntax

[lpil]

Hello!

A new syntax has been added to Gleam, the attribute syntax

@target(erlang)
pub fn main() { todo }

Attributes proceed imports or definitions in modules. The compiler only accepts @target(erlang) and @target(javascript) but I believe the tree sitter should accept any name that would be a valid function name in place of target and any comma-delimited sequence of optionally labelled constant expressions within the ().

@deprecated(since: "1.2.0", replacement: wobble)
pub fn wibble() { todo }