[CommonMark] Leading/trailing newlines are stripped in the value of fenced codeblock

[ikatyang]

Subject of the issue

commonmark: true

```


123


```

Steps to reproduce

astexplorer

Expected behaviour

Same as CommonMark playground:

{
  "type": "code",
  "lang": null,
  "value": "\n\n123\n\n"
}

Actual behaviour

 {
   "type": "code",
   "lang": null,
-  "value": "\n\n123\n\n"
+  "value": "123"
 }

Original post: prettier/prettier#5037

[alexander-akait]

/cc @wooorm looks we have a lot of bugs, maybe we can release version with fixes?

[wooorm]

@evilebottnawi Definitely! But we should also get a release out the door 🚪🛳

I’m hoping to get GH-345, GH-346, and potentially GH-321 in there though!