pest's get method and delete method lacks of a way to customize http header

[bruceauyeung]

there is a situation where demo.php try to call dest.php through pest' get method. when i start to xdebug demo.php( there is a breakpoint in it), it hangs at that point, but if have set a breakpoint at dest.php, it dont hangs at that point.
this is because neither XDEBUG_SESSION_START parameter nor XDEBUG_SESSION cookie is sent to dest.php.
please add an optional headers parameter to get and delete method, just like post and put.

[zuk]

There's a discussion about this here: #15

I haven't merged this in because there's still some disagreement about the API. Feel free to use the code from that pull request for now though, just be weary that the API may be a bit different once this functionality gets merged into this repo.