[5.4] Add includeWhen directive

[jbrooksuk]

This is a directive that shortens:

@if ($user->ownsPost($post)
@include('posts.edit-controls', ['post' => $post])
@endif

to...

@includeWhen($user->ownsPost($post), 'posts.edit-controls', ['post' => $post])

[taylorotwell]

This was merged. Not sure why it's not detecting.

[driesvints]

@taylorotwell commit hash got changed when you rebased. That's probably the reason.

[driesvints]

Not that commit authors are still kept as is. You're just now indicated as the comitter.

[seanthebean]

Found the commit that added this into the 5.4 branch, just for traceability: 5fe39aa