Incorrect number of surrounding backticks in code span with consecutive backticks

[graphemecluster]

Describe the bug

dprint-plugin-markdown version: 0.20.0

Input Code

In PowerShell, special characters are escaped using backticks:

- New line: `` `n ``

...

- Backtick: ` `` ` or ``` `` ```

Expected Output

In PowerShell, special characters are escaped using backticks:

- New line: `` `n ``

...

- Backtick: ` `` ` or ` `` `

Actual Output

In PowerShell, special characters are escaped using backticks:

- New line: `` `n ``

...

- Backtick: `` `` `` or `` `` ``

Discussion

The minimal number of backticks required to enclose the code block is the next available integer number of backticks.

For example, if the content of the code block is

` `` ````

Start from 1, it searches for the next number of consecutive backticks that the code block does not contain, which is 3 in this case. Therefore, 3 backticks are required to enclose this code block.

In the PowerShell example, only 1 backtick is required because there are no lone backtick within the code block.