Don't use self-invoking anonymous functions when generating blocks on JavaScript

[GearsDatapacks]

Currently, this gleam code:

pub fn main() {
  let a = {
    let b= 1
    b + 1
  }
}

Compiles to this javascript:

export function main() {
  let a = (() => {
    let b = 1;
    return b + 1;
  })();
  return a;
}

This isn't ideal as it creates an anonymous function which is immediately invoked, which makes the code harder to read and adds the overhead of allocating a function, calling it, then deallocating it. It would be nice to not have to do this.

Perhaps Louis has a particular alternative in mind, but we could generate something like:

let _block;
{
  let b = 1;
  _block = b + 1;
}
a = _block;
return a;

(Or in this case assign directly to a instead of _block, but I'm not sure the compiler would be able to do that)

[lpil]

Yes!!