Add a template for generating new PHP files

https://shapeshed.com/vim-templates

modules/nixvim/templates/default.nix

@@ -0,0 +1,9 @@
+{
+  flake.modules.nixvim.custom.autoCmd = [
+    {
+      event = "BufNewFile";
+      pattern = [ "*.php" ];
+      command = "0r ${./php}";
+    }
+  ];
+}

modules/nixvim/templates/php

@@ -0,0 +1,3 @@
+<?php
+
+declare(strict_types=1);