Add a heading method

[adampatterson]

Adding a heading method would look a lot cleaner when Ray is heavily used.

ray()->text('Lessons')->large();
ray($lessons)->blue();

Could become

ray($lesson)->heading('Lessons');

I tried to do this with a macro and at first pass could only create the heading. I didn't immediately see how I could preserve the values in the ray() method

Ray::macro('heading', function (string $text) {
    $this->text($text);
    $this->size('lg');
});