docs: update README and examples to reflect current API

[Copilot]

Docs were referencing removed/deprecated features and missing documentation for recently shipped ones.

README

• Fixed CORS import — was shown as default import (import cors from ...), it's a named export (import { cors } from ...)
• Added missing sections: Middleware (CORS + Sessions), Route Grouping, Validation, Static Routes (app.static(), added in chore: add express so we can make fun of it #40), Native Response Cache (res.ncache()), TLS/HTTPS
• Expanded Imports section to include all available sub-packages

Examples

Replaced deprecated app.onError() → app.error() across all four examples that used the old API:

• error-handling/server.js
• middleware/server.js
• validation/server.js
• rest-api/server.js

Also updated the examples README.md table description to match.

// Before (deprecated)
app.onError((err, req, res) => { ... });

// After
app.error((err, req, res) => { ... });

[Nadhila-dot]

Told AI to handle these automatically since its a readme and examples