[mediaqueries] Add env expression support

[zDaleZ]

So, it supports calc() now, but no env() support.
When Window Overlays Control is enabled, the CSS below might useful:

#search {
    display: none;
}

@media (min-width: calc(100% + 250px - env(titlebar-area-x, 100%)) {
    /*If the free width of the title bar is longer than 250px, show the search box.*/
    #search {
        width: 250px;
        display: block;
    }
}

Or for the non-rectangular displays:

#sidebar {
    display: none;
}

@media (min-width: calc(env(safe-area-inset-left) + env(safe-area-inset-right + 800px)) {
    /*Ensure the width of safe area is enough*/
    #sidebar {
        display: block;
    }
}

Sum up my idea, it's necessary to add env() support for Media Queries, the env() is just the most useful thing for calc(). It's perfect only if both are supported.