(Navigation) Messages dropdown

***Description:***

Add a message notification dropdown which list the message notifications related to the auth user.

***Criteria:***

- add a real-time notification.
- notification criteria: If someone messages, replies to existing messages of the auth user.
- add a readme on how to use/setup the real-time tools used for this notification.

***References:***

https://zpl.io/a8Nke4g