[Enh] Refactor Blade directive setup

[klimov-paul]

Blade directive setup has been refactored:

• use Container::extend(), allowing lazy-load Blade compiler instantiation as well as correct functioning, when Blade package is not installed.

• Add 'blade.compiler' to SharedDataServiceProvider::provides(), ensuring SharedData as well as its Blade directive will be registered correctly once Blade is requested from Container

• Add the configuration for the Blade directive name, as 'shared' is too common and may conflict with other libraries.

[hivokas]

Thanks, @klimov-paul! Could you add a test please?

[klimov-paul]

Blade directive is already tested here: https://github.com/coderello/laravel-shared-data/blob/1.0/tests/SharedDataTest.php#L296

This PR is just a refactoring.

[hivokas]

I mean a test for a custom blade directive name.

[klimov-paul]

Test has been added.

[hivokas]

Thanks for the contribution!