Add Team Description to the Team Settings (#4652)

* draft

* Add Team Description to the Team Settings

* add tooltips for team description

* made changes per PM review

* add message when there is no description set in the team

* squash

webapp/components/sidebar.jsx

@@ -736,6 +736,7 @@ export default class Sidebar extends React.Component {
 
                 <SidebarHeader
                     teamDisplayName={this.state.currentTeam.display_name}
+                    teamDescription={this.state.currentTeam.description}
                     teamName={this.state.currentTeam.name}
                     teamType={this.state.currentTeam.type}
                     currentUser={this.state.currentUser}