Provide support for @includeFirst Blade directive

[bazzik]

Replaces:

@if(view()->exists('custom-template'))
    @include('custom-template')
@else
    @include('default-template')
@endif

With:

@includeFirst(['custom-template', 'default-template'])

laravel/framework#21172

The support required: completion assistance & Ctrl+Click navigation for views (similarly to how it's done for @include directive in 1st parameter).

[Haehnchen]

done