fix: mark render method in RouteResolver as optional (#3235)

js/src/common/Application.tsx

@@ -106,14 +106,21 @@ export interface RouteResolver<
    *
    * Returns the component class, and **not** a Vnode or JSX
    * expression.
+   *
+   * @see https://mithril.js.org/route.html#routeresolveronmatch
    */
   onmatch(this: this, args: RouteArgs, requestedPath: string, route: string): { new (): Comp };
   /**
    * A function which renders the provided component.
    *
+   * If not specified, the route will default to rendering the
+   * component on its own, inside of a fragment.
+   *
    * Returns a Mithril Vnode or other children.
+   *
+   * @see https://mithril.js.org/route.html#routeresolverrender
    */
-  render(this: this, vnode: Mithril.Vnode<Attrs, Comp>): Mithril.Children;
+  render?(this: this, vnode: Mithril.Vnode<Attrs, Comp>): Mithril.Children;
 }
 
 /**