Fix indentation when code block is in a list

[reakaleek]

Details

Using .EnableTrackTrivia() on the MarkdownPipeline causes extra whitespace on code blocks if they are not at the beginning of the document, e.g. in a list. The white space from the beginning of the document until the code block gets added.

Change

This change strips the indent of the code block.

Markdown

```json
{
  "key": "value"
}
```

  ```json
  {
    "key": "value"
  }
  ```

1. this is a list
   ```json
      {
        "key": "value"
      }
   ```
   1. this is a sub-list
      ```json
      {
        "key": "value"
      }
      ```

Result

[Mpdreamz]

We might want to reevaluate if we really need track trivia.

I added it to aid with ensuring line and column numbers are correct for the error message reporting but not 100÷ convinced this is needed.