[csswg-drafts] [css-support]Add in @support ' else '

gogas has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-support]Add in @support ' else ' ==
[@suppurt](https://drafts.csswg.org/css-conditional/#at-supports)

The specification says that we can test to support the property of the browser like
`@supports (animation-name: test) { }`
or test for the non-support of a specific CSS property
`@supports not ( hanging-punctuation: first ){`
But why not reduce this code to `if (){} else {}` аs in other programming languages like:
`@supports (filter: grayscale(100%)) {`
   ` img {`
        `filter: grayscale(100%)`
    `}`
`} else {`
    `img {`
        `background-image: url("/image.png");`
    `}`
`}`

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/1096 using your GitHub account