middleware matcher should support template literals

Link to the code that reproduces this issue

https://github.com/stefanprobst/issue-next-middleware-matcher

To Reproduce

1. clone https://github.com/stefanprobst/issue-next-middleware-matcher
2. pnpm install && pnpm run dev
3. see error message in console: 'Next.js can't recognize the exported config field in route "/middleware": Unsupported template literal with expressions at "config.matcher[1]".'

Current vs. Expected behavior

i would want to be able to do this:

const locales = ["de", "en"] as const;

export const config = {
  matcher: ["/", `/(${locales.join("|")})/:path*`],
};

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #26~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Jul 13 16:27:29 UTC 2
Binaries:
  Node: 18.18.0
  npm: 9.8.1
  Yarn: 1.22.19
  pnpm: 8.8.0
Relevant Packages:
  next: 13.5.4
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.2.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Middleware / Edge (API routes, runtime)

Additional context

No response

Run the linked reproduction with the documented pnpm commands and confirm the matcher validation error. Trace the middleware config matcher validation that reports unsupported template literals, then inspect existing matcher tests if available. Done means the shown template-literal matcher is accepted without the error and existing matcher validation still passes.