Multi-Resolution Adaption Documentation suggestions

[ggnewt]

URL : https://github.com/cocos-creator/creator-docs/blob/master/en/ui/multi-resolution.md

Cocos Creator is devoted committed to solving the problem...

Next, we start off by getting to know the concepts of design resolution and screen resolution, then we will go on to make understanding of learn the zooming in/out function of the Canvas component.

[xunyi0]

Thank you for the feedback, we will amend it as soon as possible.