feat(jsruntime): closures

[masnagam]

• https://legacy.cs.indiana.edu/~dyb/papers/3imp.pdf
• https://craftinginterpreters.com/closures.html
• https://www.cs.tufts.edu/~nr/cs257/archive/roberto-ierusalimschy/closures-draft.pdf

[masnagam]

we have to consider about the following example:

<script>
  let b = () => console.log(a);
</script>
<script>
  let a = 1;
  b();
</script>

this example should work. that is, the global environment record should be shared with scripts. it should be allocated on the heap.

in this ticket, we won't implement the global environment record. #221 was added for that.