[8.x] Add a wordCount() string helper

[jeroenvanrensen]

Hi everyone,

This is my first contribution to the Laravel framework.

I added a wordCount() string helper.

Now you can shorten this:

public function getWordCountAttribute(): int
{
    $text = Str::of($this->body)
        ->replace('x', 'y') // do something
        ->replace('a', 'b'); // do something else

    return str_word_count($text);
}

To:

public function getWordCountAttribute(): int
{
    return Str::of($this->body)
        ->replace('x', 'y') // do something
        ->replace('a', 'b') // do something else
        ->wordCount();
}

At least to me, this seems a lot nicer.

If this get's merged, I would like to write the corresponding docs.

Thank you!
Jeroen