Fix language matching in code directive

[jaysoo]

Request Type: docs

How to reproduce:

Component(s): misc core

Impact: small

Complexity: small

This issue is related to:

Detailed Description:

The language matching for the code directive in docs app is not working.

For example, class="lang-javascript" should match javascript but it doesn't

Other Comments:

Includes:

• Fix for the code directive
• Tests for the code directive

[mary-poppins]

Thanks for the PR! Please check the items below to help us merge this faster. See the contributing docs for more information.

• Uses the issue template (#7339)

If you need to make changes to your pull request, you can update the commit with git commit --amend.
Then, update the pull request with git push -f.

Thanks again for your help!