Correct code type in tasks/readme

tasks/readme.md

@@ -69,7 +69,7 @@ To generate a build named `ol.min.js` with the `build.json`, you would run this:
 
 To export the `ol` symbol to somewhere other than the global namespace, a `namespace` option is available. This can e.g. be useful for creating an ol3 AMD module, by simply providing a build configuration like the following:
 
-```js
+```json
 {
   "exports": ["*"],
   "namespace": "AMD",