Add task to check that Tailwind is up to date

lib/mix/tasks/tailwind/check_version.ex

@@ -0,0 +1,35 @@
+defmodule Mix.Tasks.Tailwind.CheckVersion do
+  use Mix.Task
+
+  @shortdoc "Checks the the current Tailwind version is the latest"
+  @moduledoc """
+  Checks the the current Tailwind version is the latest.
+
+  Exits with 0 if versions match, 1 if the Tailwind needs to be updated.
+  """
+
+  @impl Mix.Task
+  def run(_args) do
+    Application.ensure_all_started(:req)
+
+    current_version =
+      Application.get_env(:tailwind, :version)
+
+    latest_version_url =
+      "https://api.github.com/repos/tailwindlabs/tailwindcss/releases/latest"
+
+    latest_version =
+      Req.get!(latest_version_url).body["tag_name"]
+      |> String.replace_prefix("v", "")
+
+    if current_version !== latest_version do
+      Mix.Shell.IO.info(
+        "A new tailwind version is available: #{current_version} ==> #{latest_version}"
+      )
+
+      System.halt(1)
+    else
+      Mix.Shell.IO.info("The tailwind version is up to date (#{current_version})")
+    end
+  end
+end