Look at the list:
"php": ">=5.3.7",
"roundcube/plugin-installer": ">=0.1.5",
"pear/mail_mime": ">=1.8.9",
"pear/mail_mime-decode": "~1.5.5",
"pear/net_smtp": "dev-master",
"pear-pear.php.net/auth_sasl": ">=1.0.6",
"pear-pear.php.net/net_idna2": ">=0.1.1",
"pear-pear.php.net/net_sieve": ">=1.3.2",
"patchwork/utf8": "1.2.x"
"johndoh/contextmenu": "dev-release-2.1"
"johndoh/markasjunk2": "dev-release-1.9"
"stwa/google-addressbook": "dev-master"
"roundcube/chbox": "dev-master"
"johndoh/sauserprefs": "dev-release-1.14"
"kolab/calendar": "dev-master"
"kolab/libcalendaring": "dev-master"
"kolab/tasklist": "dev-master"
"roundcube/filters": "dev-master"
"elm/identity_smtp": "dev-master"
"roundcube/virtual_user_mapping": "dev-master"
"flanpy/drop_drag_contact": "dev-master"
"roundcube/ude_login": "dev-master"
"marneu/custom_logo": "dev-master"
"roundcube/customizr": "dev-master"
You need a comma after each line except the last line.