Add test example of code with filename

vignettes/test/quarto-features.qmd

@@ -25,6 +25,14 @@ penguins |>                                      # <1>
 1. Take `penguins`, and then,
 2. add new columns for the bill ratio and bill area.
 
+## Code filename
+
+```{.python filename="matplotlib.py"}
+import matplotlib.pyplot as plt
+plt.plot([1,23,2,4])
+plt.show()
+```
+
 ## Diagrams
 
 ```{mermaid}