Add mention support for chat rooms

[Kannaj]

[Kannaj]

Probably a way to implement this

• build a event handler in containers/ProjectChatContainer.jsx that parses the message state and sees if any word starts with @
• on sending the message to the backend server - save the message_type as mention in the project_messages table and on a parallel increment the mentions(not yet added) column in the account_projects table (the row belonging to the mentioned user)