feat: Add clean mix task

lib/mix/tasks/pre_dot_hn/clean.ex

@@ -0,0 +1,7 @@
+defmodule Mix.Tasks.PreDotHn.Clean do
+  use Mix.Task
+
+  def run(_args) do
+    PreDotHn.clean()
+  end
+end

lib/pre_dot_hn.ex

@@ -36,6 +36,20 @@ defmodule PreDotHn do
 
   def validate(other), do: {:ok, other}
 
+  def clean() do
+    "priv/static/**"
+    |> Path.wildcard()
+    |> Enum.each(fn path ->
+      if File.dir?(path) do
+        if !File.exists?(Path.join(path, ".keep")) do
+          File.exists?(path) && File.rm_rf!(path)
+        end
+      else
+        File.exists?(path) && File.rm!(path)
+      end
+    end)
+  end
+
   def run() do
     posts =
       "site/**/*.md"