Not complain with PHP >5.6

[golendercaria]

The plugin give a compatibilities with PHP 5.6 or higher, but is not the case.

When I have install the plugin and going to wp-admin/options-general.php?page=facebook_pixel_options I have a blank page and this error on error_log :

AH01071: Got error 'PHP message: PHP Fatal error: Uncaught Error: Call to undefined function FacebookPixelPlugin\Core\str_contains() in /var/www/vhosts/xxxx/httpdocs/wp-content/plugins/official-facebook-pixel/core/FacebookWordpressOptions.php:70\nStack trace:\n#0 /var/www/vhosts/xxxx/httpdocs/wp-content/plugins/official-facebook-pixel/core/FacebookWordpressSettingsPage.php(275)...

The reason of this error is str_contains is only implemented on PHP 8 : https://www.php.net/manual/en/function.str-contains.php

For the moment we solve the problem with this little fix, in my functions.php :

	if (!function_exists('str_contains')) {
	    function str_contains($haystack, $needle) {
	        return $needle !== '' && mb_strpos($haystack, $needle) !== false;
	    }
	}

[fbisaso]

This will be fixed in the next release.

f318d64