Markdown nested code blocks delimited by tildes error

Prettier 2.8.7
Playground link

--parser markdown

Input:

```markdown
**This is markdown**
~~~json
"this is json"
~~~
```

Output:

```markdown
**This is markdown**

```json
"this is json"
```
```

Expected behavior:

```markdown
**This is markdown**

~~~json
"this is json"
~~~
```

or

````markdown
**This is markdown**

```json
"this is json"
```
````

Hey Prettier crew. I was writing a blog post about how to write Markdown code blocks inside Markdown code blocks. There are multiple ways of doing this, the easiest being to use different numbers of backticks (`) for each nested code block. Another way of doing it is to use, for example, triple backticks for the outer code block and then triple tildes for the inner one. That's what I used in the example above.

The issue, though, is that Prettier is converting the triple tildes to triple backticks. With that change, my Markdown parser (GFM through Kramdown on Jekyll) is no longer able to delimit between the outer and inner code blocks.

Suggestions:

• Prettier should leave tilde-delimited code blocks inside other code blocks alone, or
• Prettier should convert the tildes into backticks and automatically increase the number of backticks in the parent code block.

Reproduce the reported case in the Prettier Playground with --parser markdown, using the nested backtick and tilde examples in the issue. Trace the Markdown formatting entry point and verify that formatting preserves a tilde-delimited inner block or safely increases the parent fence when converting it. Done when the output remains correctly delimited in the stated examples.