change 'plain' to 'pug' identifier in code blocks

[krzysztof-tokarski]

I felt like these codeblock were very hard to read, especially the first one, without any kind of syntax highlighting.

Definitely looks more readable than before, yet too bad this identifier is somewhat lazy on the highlighting, dunno if its possible to achieve something closer to what I have in VSC (highlighting for html tags!)

EDIT:
Def would also alter the codeblock found in here:
https://developer.mozilla.org/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data/LocalLibrary_base_template

[github-actions]

Preview URLs

• https://pr18744.content.dev.mdn.mozit.cloud/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data/Template_primer

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data/Template_primer
Title: Template primer
on GitHub

No new external URLs

[hamishwillee]

Thank you but pug is not supported by the MDN renderer, so this is pointless (otherwise we'd already use it. You can see it still renders as plain: https://pr18744.content.dev.mdn.mozit.cloud/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data/Template_primer

Prism supports pug and I have asked about this in mdn/yari#6763 - I'm closing for now because this is probably not going to be a priority, and won't be done if it is "costly"

[krzysztof-tokarski]

Oh you're right. I seemed to have some highlighting when previewing on GH but it's gone in that read only view. Too bad