Update README.md with full hello_world.asm.js source

This tripped me up as a complete beginner, since I had copied out the example code from the README rather than the test file.

1 files changed, 4 insertions, 0 deletions

diff --git a/README.md b/README.md
index 24717c3f1..b04942f19 100644
--- a/README.md
+++ b/README.md
@@ -93,11 +93,15 @@ $ bin/asm2wasm test/hello_world.asm.js
 That input file contains
 
 ```javascript
+function () {
+  "use asm";
   function add(x, y) {
     x = x | 0;
     y = y | 0;
     return x + y | 0;
   }
+  return { add: add };
+}
 ```
 
 You should see something like this: