[feature request]Whether or not you can add parameters to the RouterEntry

[qcks]

hello.

I'm a newbie. Would like to count interfaces where 'content-type' is 'text/html' after the service startup route is loaded.

RouterEntry adds the parameter content-type, which is used to learn the type of data to be transmitted as early as possible as a result of routing.

I don't know if it's feasible.

    RouterEntry(
      String verb,
      String route,
      Function handler, {
      Middleware? middleware,
      String? contentType//?
  })