[7.x] Implement env and production Blade directives

[driesvints]

I often find myself doing this:

@if (app()->environment('production'))
    <!-- Some tracking code here -->
@endif

This pr allows for:

@production
    <!-- Some tracking code here -->
@endproduction

And also for more granular environment checking if needed:

@env('staging')
    <!-- Some tracking code here -->
@endenv

[SjorsO]

The docs have an example of a custom @env directive. The example should probably be changed if this gets merged.

[julienbourdeau]

I keep adding this custom directive to my project so that would be very useful! Plus, custom directive breaks the syntax coloring and open/close pairs 😄

Thank you Dries! 👏

[linaspasv]

I keep adding this custom directive to my project so that would be very useful! Plus, custom directive breaks the syntax coloring and open/close pairs 😄

Thank you Dries! 👏

No, it does not break the syntax coloring if you are using it correctly. You should close it using @endenv.

[driesvints]

Thanks everyone. I've sent in a PR to update the existing docs example: laravel/docs#6043