Feature: Add `Router` Support

[ItzNotABug]

1. This PR adds the ability to use a Router, something like -

   const appExpress = new AppExpress();
   const router = new AppExpress.Router();
   
   router.get('/sub', (...) {});
   router.post('/sub', (...) {});
   router.patch('/sub', (...) {});
   
   appExpress.use('/', router);

2. Additional changes include perf. side improvements by replacing Array implementations with Map for fast access.

3. Implement tests, add a GitHub Workflow for PRs for the same

4. Middleware registry is now via appExpress.middleware(...) and not appExpress.use(...)

5. Middlewares now run before finding any routes and can also return responses now

[ItzNotABug]

I think we should keep the AppExpressResponse in the middleware handler.

This will be helpful for supporting external middlewares.

[ItzNotABug]

Tests run fine -

[ItzNotABug]

LGTM, can be merged. Live Action @ https://appexpressdev.appwrite.global.