Provide better Type support.
Not only for express, but also fastify, next.js, etc...

Related issues

• fix(types): make request & response generic and remove express dependency #478
• Move @types/express to dependencies #683
• Type regression (express.Request -> http.IncomingMessage) #692
• Breaking change in 2.0.1 #650
• chore(typescript): extract handlers types #603
• ResponseInterceptor recipe types mismatch #632
• Expose HTTP Proxy middleware, so it can be used outside express #687
• fix(types): fix type regression #700
• responseInterceptor uses more constrained types than onProxyRes provides #708
• TypeScript regression in 2.0.3 #713
• Handler types are incorrectly coupled to express.js #719