Missing COMPILE pragmas for JavaScript

[rintcius]

module HelloWorld where

open import IO
open import Data.String
open import Data.Unit
open import Level using (0ℓ)

main = run {0ℓ} (putStrLn "Hello World!")

This prints Hello World! with --compile but with --js it doesn't print anything.

Tested running it with: NODE_PATH=. node jAgda.HelloWorld.js

Agda version: a51ad95196ee60a19835c35e20e782c6ab6428e0

[gallais]

IO.Primitive only gives bindings for the GHC backend.

I am not planning to look into adding javascript support but if people want to work
on this, I have no objection to it being merged in the stdlib.