Include css and js in Dawn theme

I think I understand that with the Dawn template, all the JS files are minified in the main.min.js files and the CSS in the screen.css in the build folder.

Now I’m working without using standard development tools like yarn. So to modify the CSS I directly edit the screen.css file in the build folder.

Now I would like to add a new .css file and a new .js file, but I would like to include them only in some files like post.hbs and page.hbs.

How can I solve?

Also I can’t find the page.hbs file like in all other themes, there is only post.hbs, how can I customize the pages?