No code syntax highlighting on documentation rendered from discourse

[grobbie]

Summary

In discourse, code listings in documentation can have interpreter specific code highlighting applied, which renders, for example in discourse.charmhub.io. However, whent the same document is rendered on ubuntu.com, the code highlighting is lost, making the code harder to read. see for example: https://discourse.charmhub.io/t/create-mtls-client-credentials/11079 versus https://ubuntu.com/data/docs/kafka/iaas/t-create-mtls-client-credentials

The syntax highlighting should also be applied on ubuntu.com