:sparkles: added artst<->event and artist<->exhibition

plugins/cia-post-types/includes/p2p-mappings.php

         'reciprocal' => true,
         'admin_box' => $admin_box
     ]);
+    p2p_register_connection_type([
+        'name' => 'artists_to_exhibitions',
+        'to' => 'artist',
+        'from' => 'exhibition',
+        'reciprocal' => true,
+        'admin_box' => $admin_box
+    ]);
+    p2p_register_connection_type([
+        'name' => 'artists_to_events',
+        'to' => 'artist',
+        'from' => 'event',
+        'reciprocal' => true,
+        'admin_box' => $admin_box
+    ]);
 
     p2p_register_connection_type([
         'name' => 'episodes_to_exhibitions',