chore: create and add plugin template

created with help by these Websites:
[Delicious Brains](https://deliciousbrains.com/wordpress-plugin-development-template-files/)
[Wordpress Plugin Boilerplate generator](https://wppb.me/)

rk-wichteln/admin/partials/rk-wichteln-admin-display.php

@@ -0,0 +1,16 @@
+<?php
+
+/**
+ * Provide a admin area view for the plugin
+ *
+ * This file is used to markup the admin-facing aspects of the plugin.
+ *
+ * @link       https://wpdev.rainer-kehnen.de
+ * @since      1.0.0
+ *
+ * @package    Rk_Wichteln
+ * @subpackage Rk_Wichteln/admin/partials
+ */
+?>
+
+<!-- This file should primarily consist of HTML with a little bit of PHP. -->