content: Add twitter and other channels

Relate-to: eclipse-wg/oniro-wg/proposal-incubation-stage-oniro/proposal-incubation-oniro-marketing#18

Signed-off-by: Philippe Coval <philippe.coval@huawei.com>

content/join-us/_index.md

@@ -4,8 +4,10 @@ seo_title: "Join Oniro Working Group"
 keywords: ["join Oniro", "Oniro", "open source", "working group"]
 ---
 
-* [Community's chat](https://docs.oniroproject.org/en/latest/community-chat-platform.html)
+* [Public developers mailing list](https://accounts.eclipse.org/mailing-list/oniro-dev)
 * [Public working group's mailing list](https://accounts.eclipse.org/mailing-list/oniro-wg)
+* [Community's chat](https://docs.oniroproject.org/en/latest/community-chat-platform.html)
+* [Follow Oniro on Twitter](https://twitter.com/@oniro_project)
 * [Contact Oniro's staff](https://oniroproject.org/join-us/)
 
 {{< hubspot_contact_form portalId="5413615" formId="1279b5cf-d70f-4977-b585-b6885fac1d75" >}}