added <developer> section to documentation section
added <developer> section to documentation section

according to https://doc.owncloud.org/server/9.0/developer_manual/app/info.html
jsxc/jsxc.owncloud,owncloud/jsxc.chat,owncloud/jsxc.chat,jsxc/jsxc.owncloud,jsxc/jsxc.owncloud,owncloud/jsxc.chat