Add config endpoint

lib/mobilizon_web/resolvers/config.ex

@@ -0,0 +1,14 @@
+defmodule MobilizonWeb.Resolvers.Config do
+  @moduledoc """
+  Handles the config-related GraphQL calls
+  """
+  require Logger
+  import Mobilizon.CommonConfig
+
+  @doc """
+  Get config
+  """
+  def get_config(_parent, _params, _context) do
+    {:ok, %{name: instance_name(), registrations_open: registrations_open?()}}
+  end
+end