chore(i18n): Fix/add proper translator comments (#2716)

Co-authored-by: Brandon <brandon@tendency.me>

bootstrap/app.php

@@ -29,6 +29,7 @@ collect(['helpers', 'setup', 'filters', 'admin'])
     ->each(function ($file) {
         if (! locate_template($file = "app/{$file}.php", true, true)) {
             wp_die(
+                /* translators: %s is replaced with the relative file path */
                 sprintf(__('Error locating <code>%s</code> for inclusion.', 'sage'), $file)
             );
         }