[9.x] Add disabled directive

[belzaaron]

This PR provides the use of the common HTML directive disabled through a shorthand syntax via a Blade directive. Allowing developers to have a more enjoyable method of disabling a button, for example, could improve the smooth flow that we Laravel developers are consistently being treated too. Simple yet, effective.

<button type="submit" @disabled($errors->isNotEmpty())>Submit</button>

Editing for documentation PR: laravel/docs#7690

[bogdankharchenko]

I feel like I've been seeing a few of these new form related blade helpers -- but sometimes I wonder is this ultimately becoming a form builder?

I'm not strongly opposed to this but I wonder if we need these additional blade helpers... @readonly next week?

This is a form builder for example, which uses components/functions to define the form structure in an elegant way instead - maybe this is the solution for some people and it could perhaps could prevent a dozen more PR's for form related directives.
https://github.com/glhd/aire#blade-components