Update README.md

### LDAP Contacts 

If you enable LDAP_CONTACTS, then all users in LDAP_GROUP_FILTER are loaded from the ldap server into the contacts. 

If you enable LDAP_CONTACTS, then all users in LDAP_USER_FILTER are loaded from the ldap server into the contacts. 

At the moment this happens every time you click on "Share" within a project.

The user search happens without bind - so if your LDAP needs a bind you can adapt this in the 

function `getLdapContacts()` in ContactsController.js (line 92) 

if you want to enable this function set:

```

LDAP_CONTACTS: 'true'

LDAP_GROUP_FILTER: '(memberof=GROUPNAME,ou=groups,dc=DOMAIN,dc=TLD)'

```

### Sharelatex Configuration