[Bug] Syntax highlighting is not case-sensitive

[guoqqqi]

Describe the bug

Code block highlighting in markdown is not case-sensitive.

When I tag a code block with Lua the block is not highlighted, when I change it to lua it is highlighted.

To reproduce

Steps to reproduce the behavior:

1. Create a new Markdown article
2. Edit the contents of the code block and mark it as Lua
3. Posting Updates
4. See error

Expected behavior

I can highlight Markdown code blocks using either Lua or lua tags