Support `flex-basis: fill-available(stretch)`

TODO


## Input

```css
.foo {
   flex-basis: stretch;
}
```

## Expected

Note: Chrome does not implement `flex-basis: -webkit-fill-available`!

```css
.example {
   flex-basis: -webkit-fill-available; /* Safari */
   flex-basis: -moz-available;
   flex-basis: stretch;
}
```