feat(chat): order chats by their names

This is achieved by improving `Ecto.Query` usage.

lib/slax/chat.ex

@@ -9,8 +9,8 @@ defmodule Slax.Chat do
   alias Slax.Repo
 
   def get_first_room! do
-    query = from(r in Room, limit: 1)
+    query = from(r in Room, limit: 1, order_by: [asc: :name])
-    Repo.one(query)
+    Repo.one!(query)
   end
 
   def get_room!(id) do
@@ -18,6 +18,7 @@ defmodule Slax.Chat do
   end
 
   def list_rooms do
-    Repo.all(Room)
+    query = from(r in Room, order_by: [asc: :name])
+    Repo.all(query)
   end
 end