Slightly improve experimental.mdxRs error message with Webpack (#68356)
This is of course still not great. Is there a way/will to have
codeframes similar to https://github.com/vercel/turbo/pull/8879 when
using Webpack?
Before:
```
Error: page.mdx:Error: Message { place: Some(Point(7:1 (87))), reason: "Unexpected end of file in expression, expected a corresponding closing brace for `{`", rule_id: "unexpected-eof", source: "markdown-rs" }
Import trace for requested module:
./app/blog/hello-world/page.mdx
⨯ ./app/blog/hello-world/page.mdx
```
After:
```
Error: page.mdx:Error: 7:1: Unexpected end of file in expression, expected a corresponding closing brace for `{` (markdown-rs:unexpected-eof)
Import trace for requested module:
./app/blog/hello-world/page.mdx
⨯ ./app/blog/hello-world/page.mdx
```