A Fully Runnable HTTP Demo

[LintaoAmons]

https://github.com/LintaoAmons/kulala-http-runable-demo

[LintaoAmons]

I think this kind of demo is more straightforward for people to use as a reference(easier to copy/paste),
if you feel it is worth a PR(maybe find a place to put it), I can create one~

[YaroSpace]

I think it is a great idea. Please make a PR and allow contributors to edit, so I can integrate it into docs.