add const TwitterStrategy

lib/service/passport.js

@@ -4,6 +4,7 @@ const LocalStrategy = require('passport-local').Strategy;
 const LdapStrategy = require('passport-ldapauth');
 const GoogleStrategy = require('passport-google-auth').Strategy;
 const GitHubStrategy = require('passport-github').Strategy;
+const TwitterStrategy = require('passport-twitter').Strategy;
 
 /**
  * the service class of Passport