Shorter way to write a Spread Operator in a array for null value

### Description

add a new writing possibility, so that :
```php
$array = [...($var !== null) ? ['key' => $var] : []];
```
could be shortened to 
```php
$array = ['key' ?=> $var];
```

So , if `$var = null; ` then `$array` would result to `[]`
and if `$var = false;` then `$array` would result to`['key' => false]`

_( same as using an array_merge() + array_filter() )_