My custom plugin creates a custom post type, and I want to theme my own
"single-my_custom_cpt.php" file. However, I want to store it in my plugin folder, and allow that it be over-written in the websites' active theme folder.
For example, single-my_custom_cpt.php exists in
/plugins/my-plugin/ folder, and someone creates
/themes/site-theme/single-my_custom_cpt.php. I want the theme file to come up first, and if it's deleted, the plugin file to come up.