public function css($css) {
        $css = trim($css);
        if (substr($css, -1) !== ';') {
            $css = $css . ';';
        }
        return $this->att(['style' => $css]);
    }
public function css($css) {
        $css = trim($css);
        if (substr($css, -1) !== ';') {
            $css = $css . ';';
        }
        return $this->att(['style' => $css]);
    }
public function css ( $ css ) { $ css = trim ( $ css ) ; if ( substr ( $ css , - 1 ) !== ';' ) { $ css = $ css . ';' ; } return $ this -> att ( [ 'style' => $ css ] ) ; }
Add custom style for the icon

Example:
echo FA::check('ok')->css('padding-right:20px');
echo FA::check('ok', FA::FA_ROT90&FA::FA_SPIN)->css('padding-right:20px');

@param $css string
@return static
Add custom style for the icon