Code highlighting language specifier is case sensitive

[juls0730]

here:

mdc/src/runtime/highlighter/shiki.ts

Line 78 in 85ac40a

const highlighter: Highlighter = async (code, lang, theme, options = {}) => {

lang is never normalized (e.g. .toLowerCase()), and has given me problems when I use TS (uppercase) for the codeblock instead of ts (lowercase). Perhaps we should normalize lang.