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/uninstall.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * Fired when the plugin is uninstalled.
+ *
+ * When populating this file, consider the following flow
+ * of control:
+ *
+ * - This method should be static
+ * - Check if the $_REQUEST content actually is the plugin name
+ * - Run an admin referrer check to make sure it goes through authentication
+ * - Verify the output of $_GET makes sense
+ * - Repeat with other user roles. Best directly by using the links/query string parameters.
+ * - Repeat things for multisite. Once for a single site in the network, once sitewide.
+ *
+ * This file may be updated more in future version of the Boilerplate; however, this is the
+ * general skeleton and outline for how the file should work.
+ *
+ * For more information, see the following discussion:
+ * https://github.com/tommcfarlin/WordPress-Plugin-Boilerplate/pull/123#issuecomment-28541913
+ *
+ * @link       https://wpdev.rainer-kehnen.de
+ * @since      1.0.0
+ *
+ * @package    Rk_Wichteln
+ */
+
+// If uninstall not called from WordPress, then exit.
+if ( ! defined( 'WP_UNINSTALL_PLUGIN' ) ) {
+	exit;
+}