merging other routers to appRouter

// router/router.ts
import type { Context } from '$server/trpc/context';
import { initTRPC } from '@trpc/server';

export const tRPC = initTRPC.context<Context>().create();

export const publicProcedure = tRPC.procedure;
export const appRouter = tRPC.router;

export type AppRouter = typeof appRouter;

// routers/user.ts
import { appRouter, publicProcedure } from '$server/trpc/router';

export const userRouter = appRouter({
    list: publicProcedure.query(() => {
        return [];
    })
});