Add a way to access available param-matchers from inside a library

Describe the problem

It's currently not possible to access the param-matcher-functions that are available in an App from inside a library. They need to be passed into the library by reference, one-by-one.

I have a library that requires access to the matcher-functions as it operates on routeIDs.

Having to pass matchers to the library one-by-one is cumbersome and error-prone since you're likely to forget to add new matchers
vite-glob-imports don't work since they don't respect kit.files.params

As discussed in: https://discord.com/channels/457912077277855764/1226858732223205497/1226858732223205497

Describe the proposed solution

A way to access the matcher-functions that are present in an app. For example an $app/matchers module where we can import the matcher functions from. Given that matchers are already shipped to the client this wouldn't make a meaningful bundle-size difference, it's just about exposing them.

Example:

import * as matchers from "$app/matchers"

matchers.int("123") // true
matchers.float("asd") //false

const availableMatchers = Object.keys(matchers) // ["int", "float", "uuid"]

Alternatives considered

Require library users to pass in matcher-functions one by one. This is awkward since they'er all exported as "match" and the matcher name is implicit from the filename.

import { init } from "some-library"
import { match as int } from "../params/int.js"
import { match as float } from "../params/float.js"

init({ matchers: { int, float }})

Importance

nice to have

Additional Information

No response

sveltejs / kit