Make render available on ctx.response

[rkt2spc]

Allow cleaner usage with koa:

exports.foo = async ({ request, response }, next) => {
    await response.render('foo/bar');
};

[int64ago]

Hi, why not use render from ctx directly, like this:

exports.foo = async ({ request, response, render }, next) => {
    await render('foo/bar');
};

[rkt2spc]

I think it's more intuitive this way. Imagine a lot of other APIs that have to be spread, the ctx object will be bloated.

[int64ago]

I will publish it with v6.1.4 later, thanks again!