bug: indented codeblock is not rendered correctly

[sushichan044]

Context:

• version (md-to-pdf -v):5.1.0
• platform (Unix, macOS, Windows): Ubuntu 20.04 on WSL2
• node version: v16.14.2

When I convert md to pdf,
As shown in the image, All indented code block is not rendered correctly and the inside is transparent.
Regardless of which CSS I use.
But inline codes are displayed correctly.

[simonhaenisch]

thanks for the report. until i have time to look into it, you can used fenced code blocks instead of indented ones as a workaround.

```
code here
```