markdownlint/doc-build/md040.md

This rule is triggered when fenced code blocks are used, but a language isn't specified:

```
#!/bin/bash
echo Hello world
```

To fix this, add a language specifier to the code block:

```bash
#!/bin/bash
echo Hello world
```

To display a code block without syntax highlighting, use:

```text
Plain text in a code block
```

You can configure the allowed_languages parameter to specify a list of languages code blocks could use. The default value is [] which means any language specifier is valid.

Rationale: Specifying a language improves content rendering by using the correct syntax highlighting for code. More information: https://cirosantilli.com/markdown-style-guide#option-code-fenced.