[Feature Request] Add router example

[JohannLai]

I will write a radix-base router with deno, some fast router repo:

• https://github.com/delvedor/find-my-way
• https://github.com/charlieduong94/radix-router

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[JohannLai]

Koa tree router: https://github.com/steambap/koa-tree-router