[minify] Do not convert `rotate: 0deg` to `rotate: none`

[yisibl]

The specification clearly states that rotate: 0deg creates a stacking context and containing block, while rotate: none does not.

See Demo: https://codepen.io/yisi/pen/QwEJEmr?editors=0100

All three properties accept (and default to) the value none, which produces no transform at all. In particular, this value does not trigger the creation of a stacking context or containing block for all descendants, while all other values (including “identity” transforms like translate: 0px) create a stacking context and containing block for all descendants, per usual for transforms.
https://drafts.csswg.org/css-transforms-2/#valdef-translate-none

input

.foo {
    rotate: 0deg;
}

output

.foo{rotate:none}

expected

.foo{rotate:0deg}

Note: The unit “deg” cannot be omitted.