Add support for `meta` field on `Code` blocks

[Heziode]

In the section code in the README we have the following example:

```javascript highlight-line="2"
foo()
bar()
baz()
```

Expected: it should give something like this:

{
  type: 'code',
  lang: 'javascript',
  meta: 'highlight-line="2"',
  value: 'foo()\nbar()\nbaz()'
}

Actual: we take this instead:

{
  type: 'code',
  lang: 'javascript highlight-line="2"',
  value: 'foo()\nbar()\nbaz()'
}

[wooorm]

I think you‘re talking about remark, the parser that creates mdast, right?
In that case, I merged the PR for this today. It’ll be released soon with the new changes.

[Heziode]

I think you‘re talking about remark, the parser that creates mdast, right?

Yes, I just realized…

In that case, I merged the PR for this today. It’ll be released soon with the new changes.

Great, this can maybe unlock zestedesavoir/zmarkdown#255