feat(store): add shard supervisor

lib/excache/store/supervisor.ex

@@ -0,0 +1,21 @@
+defmodule Excache.Store.Supervisor do
+  @moduledoc false
+
+  use Supervisor
+
+  def start_link(_arg) do
+    Supervisor.start_link(__MODULE__, :ok, name: __MODULE__)
+  end
+
+  @impl true
+  def init(:ok) do
+    count = Excache.Store.shard_count()
+
+    children =
+      for index <- 0..(count - 1) do
+        Supervisor.child_spec({Excache.Store.Shard, {index, count}}, id: {:shard, index})
+      end
+
+    Supervisor.init(children, strategy: :one_for_one)
+  end
+end