Setup Dialyxir and Credo code analyzers:

- Refactor codebase according to analyzers

lib/url/repo/ets.ex

@@ -1,4 +1,8 @@
 defmodule Shortnr.URL.Repo.ETS do
+  @moduledoc """
+  This module is an implemention of the Repo behaviour using the Erlang ETS library.
+  """
+
   @behaviour Shortnr.URL.Repo
 
   @impl true
@@ -16,7 +20,7 @@ defmodule Shortnr.URL.Repo.ETS do
   end
 
   @impl true
-  def list() do
+  def list do
     resp = ets().select(:urls, [{:"$1", [], [:"$1"]}])
     {:ok, resp |> Enum.map(&elem(&1, 1))}
   end

lib/url/repo/repo.ex

@@ -1,6 +1,11 @@
 defmodule Shortnr.URL.Repo do
-  alias Shortnr.URL
+  @moduledoc """
+  This module defines the Repo behaviour for the URL service. All Repos must implement this
+  entire behaviour.
+  """
+
   alias Shortnr.Transport
+  alias Shortnr.URL
 
   @callback put(URL.t()) :: :ok | Transport.error()
   @callback get(String.t()) :: {:ok, URL.t()} | Transport.error()