use hooks instead of patching themes to show ai credits

ai-credits.php

+<?php
+/*
+ * Plugin Name: A/I - Credits
+ * Description: Show Autistici/Inventati credits in some themes' footers
+ * Version: 0.0.1
+ * Author: Autistici/Inventati
+ * Author URI: https://autistici.org
+ */
+
+function ai_footer_credits(){    
+    echo '<strong><a href="https://noblogs.org">Noblogs</a> is a project of <a href="https://www.autistici.org">R*</a></strong> | ';
+}
+
+# defines a custom action hook, to be used when patching themes
+# use this by adding in the footer.php file of the theme, at the appropriate location (usually before/after "Powered by Wordpress")
+# <?php do_action( 'ai_credits' ); ?>
+add_action('ai_credits', 'ai_footer_credits');
+
+# ten does have a _credits hook, but it not work nicely due to annoying image background to <a> elements set in the CSS of the theme
+foreach (array('eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen') as $year){
+    add_action('twenty' . $year . '_credits', 'ai_footer_credits');
+}
+
+
+?>