[feat] TrailingCommaInMultiLineArrayFixer

|Q            |A  |
|---          |---|
|Bug Fix?     |n  |
|New Feature? |yes|
|BC Breaks?   |n  |
|Deprecations?|n  |
|Tests Pass?  |yes|
|Fixed Tickets|   |
|License      |MIT|
|Doc PR       |   |
                   

This adds the TrailingCommaInMultiLineArrayFixer: PHP Multi-line arrays should have a trailing comma

There is only minor problem that I was unable to resolve, when you have an array like.

```php
<?php

$x = array(
    array());

?>
```

The result will be.

```php
<?php

$x = array(
    array(),);

?>
```

Which is not fully correct, but the detection for this is problamatic.

We can't just add a new line, as that will move the closing brace to the beginging of the line.
And looking for the previous whitespace as something like `($y ? 'yes' : 'no')` will detect the wrong whitespace for indenting.

So we can either detect the missing new-line and add it, and let a nother fixer (or manual change) fix this.
Or leave this as it is now, and try to fix this later using either another fixer or improving this fixer.

Sent using [Gush](https://github.com/gushphp/gush)
the reverse iteration is not needed here, and it would be much more efficient to iterate forward starting at the index you consider, given that it avoids looping over lots of useless code at the end.

Thus, I thikn the implementation is broken currently: you stop the loop as soon as the brace level is 0, but starting to look at it at the end of the source. This means that is very likely that you won't fix the array at the provided index (if the last token of the file is not a brace, you will exit immediately). Add a test with a code usign something else after the array and you will see it.