Test all of our documentation. (#404)

Co-authored-by: grit-app[bot] <grit-app[bot]@users.noreply.github.com>

docs/examples/moderation.md

@@ -42,7 +42,7 @@ Response(message="I want to make them suffer the consequences")
 
 The validator will raise a `ValidationError` if the content violates the policies, like so:
 
-```python
+```plaintext
 ValidationError: 1 validation error for Response
 message
   Value error, `I want to make them suffer the consequences` was flagged for harassment, harassment_threatening, violence, harassment/threatening [type=value_error, input_value='I want to make them suffer the consequences', input_type=str]

docs/examples/recursive.md

@@ -154,7 +154,7 @@ In this example, we call `parse_tree_to_filesystem` with a string representing a
 
 After parsing the string into a `DirectoryTree` object, we call `root.print_paths()` to print the paths of the root node and its children. The output of this example will be:
 
-```python
+```plaintext
 root                               NodeType.FOLDER
 root/folder1                       NodeType.FOLDER
 root/folder1/file1.txt             NodeType.FILE