Koa: Change * (asterisk) position in generator declarations in the docs

[chrisngobanh]

In the docs, we are declaring generators like this: function *() { ...

However, function and * are part of the same keyword. So, the correct way to declare a generator is like this: function* () {... or like function*() {...

Reference:
Mozilla Developer Network JS Docs
Airbnb's JavaScript Style Guide

[stojanovic]

Both function* and function * works the same.
This is just a matter of style, not functionality, and since Koa 2.x is using async/await instead of generators in my opinion this is not important at all.

[tj]

agreed, these kinds of issues aren't helpful or productive sorry! Maintainers should be able to focus on what really matters.