Update prefixfree.dynamic-dom.js

[simonkcleung]

Fix to https://github.com/LeaVerou/prefixfree/issues/120

[LeaVerou]

Hi there, Thanks and sorry for the huge delay. What is this PR about? There seems to be very little explanation and a very large diff.

[simonkcleung]

Line 58, Line 63

Checking (prefixed in proto) is not correct because proto is not a list of CSS properties.

The prototype of style "proto" in Chrome/Edge: document.documentElement.style.constructor = CSSStyleDeclaration(){} in FF: CSS2Properties(){} in IE: MSStyleCSSProperties(){}

List of CSS properties: Object.getOwnPropertyNames of in FF: proto.prototype in Chrome/IE: document.documentElement.style

Setting of unprefixed properties to proto:

Prefix in FF is e.g. MozAnimation in Chrome : webkitAnimation in Edge: webkitAnimation and msAnimation??? in IE: msAnimation

Need further review for Edge.

The getter and setter functions could be placed outside the for loop for better performance.