No. package.json dependencies are installed into node_modules, that's just the way it is.
You could always manually download the css or javascript and place it in your public directory.. or use your own script(s) to copy the relevant file(s) after they're install via npm/yarn (an npm script would work for that). Or you could use yeoman or bower, etc.
There are lots of ways to skin this cat, and nothing is forcing you to use npm/yarn.. if fact if you're not using webpack, gulp, elixir or another build tool there's really no reason you should be using the package.json and npm/yarn at all.