[8.x] Adding lang_path helper function

[rrpadilla]

Based on the PR #36044 the framework will look for the lang directory in both the "resources" directory and at the top level.

Adding a new helper function lang_path to get the current path to the language folder.

$langPath = lang_path(); // PROJECT_DIR/resources/lang or PROJECT_DIR/lang

$langPath = lang_path('es'); // PROJECT_DIR/resources/lang/es or PROJECT_DIR/lang/es

$langPath = lang_path('en'); // PROJECT_DIR/resources/lang/en or PROJECT_DIR/lang/en

Using a custom directory. Don't have to figure it out where is the lang directory.

// Set the language file directory.
app()->useLangPath(resource_path('language'));

$langPath = lang_path(); // PROJECT_DIR/resources/language

$langPath = lang_path('es'); // PROJECT_DIR/resources/language/es

$langPath = lang_path('en'); // PROJECT_DIR/resources/language/en