Make regex more robust for checking URL


We need to improve regex for URL in "plugin_header_invalid_plugin_uri_domain". Following was not detected:

- https://example.com
- https://www.example.com/

Ref:

```php
preg_match( '/\/\/(example\.com|example\.net|example\.org)\//', $plugin_header['PluginURI'], $matches )
```

Also, this check seems to be missing for "Author URI" header.