I am fairly new to WordPress development and making a plug-in just for a fun personal project. I have taken some tutorials and am trying to do everything the best way possible. I have a CPT I created as part of the plug-in that has custom metadata fields. So I had to create a template page in order to display those metadata fields.
What I can't seem to figure out or properly google is how to get my new template page to know about and incorporate the site's theme CSS classes. I would like it to be theme-agnostic so it looks like the default single template regardless of which theme is being used. Is there a way to say, for example, H2 headers should all copy their CSS classes from some other source? Or maybe to just extend the existing single template without creating a totally separate replacement? Or is my best bet just to create a companion theme to go with my plug-in and recommend they always be used together lest there be differences in the post type presentation?