Root composer.json requires PHP extension ext-intl * but it is missing from your system. Install or enable PHP's intl extension.
php -v
in php.ini:
if php version == 5.6 version (check version using php -v)
;extension=php_intl.dll
; remove semicolon
extension=php_intl.dll
For php.ini 7.* version
if php version == 7.x:
;extension=intl
; remove semicolon
extension=intl