Git merge conflict tag detection

[morganrowse]

I think it would be helpful to detect when a user forgets to remove a git merge conflict tag like below:

$myCoolArray = [
    'first_name' => 'Bob',
<<<<<<< HEAD
    'last_name' => 'Henry',
=======
    'last_name' => 'Smith',
>>>>>>> master
];

It looks like this sniff will be added in a future version of phpcs as seen in the link below.

squizlabs/PHP_CodeSniffer@c961b32