Update Parser type for optional loose arg

The default parser accepts this, and behaves differently when it's passed (e.g., it's needed for nested routes) so it seems useful to include in typing.

packages/wouter/types/router.d.ts

@@ -5,7 +5,10 @@ import {
   BaseSearchHook,
 } from "./location-hook.js";
 
-export type Parser = (route: Path) => { pattern: RegExp; keys: string[] };
+export type Parser = (
+  route: Path,
+  loose?: boolean
+) => { pattern: RegExp; keys: string[] };
 
 export type HrefsFormatter = (href: string, router: RouterObject) => string;