Auto detect lang directories in module root

[gehrisandro]

First, thanks a lot for the package @inxilpro 🥳

This PR allows the lang directory to be in the module root besides the currently required nesting within the resources directory.

With this change, we can have the same directory structure as Laravel has introduced in version 9: https://laravel.com/docs/9.x/upgrade#the-lang-directory

Before:

resources/
  lang/
    en/
      page-1.php
      page-2.php

After:

lang/
  en/
    page-1.php
    page-2.php

// or

resources/
  lang/
    en/
      page-1.php
      page-2.php

This is a non-breaking change.