minor fixes

Author: iliakan

1-js/01-getting-started/01-hello-javascript/article.md

@@ -12,8 +12,12 @@ Technically, even a coffee machine can include its own JavaScript engine to allo
 
 ![](javascript-engine.svg)
 
+```smart header="Where to read?"
 There's a formal language description called [ECMAScript Language Specification](https://tc39.es/ecma262/), it describes how a JavaScript engine works. Sometimes we'll give references to it, but, though technically correct, it's hard to read for humans.
 
+Also, there's a good JavaScript reference at [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference). One can type `mdn <a javascript term>` in an internet search engine to find the information about that term there.
+```
+
 Programs in JavaScript are called "scripts". 
 
 **In this tutorial we concentrate on the "core" JavaScript, that works mostly everywhere.**