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

i18n/en.json

@@ -3771,6 +3771,10 @@
     "id": "model.team.is_valid.name.app_error",
     "translation": "Invalid name"
   },
+  {
+    "id": "model.team.is_valid.description.app_error",
+    "translation": "Invalid description"
+  },
   {
     "id": "model.team.is_valid.reserved.app_error",
     "translation": "This URL is unavailable. Please try another."