HTML+ engine allows you to specify a Typescript file in your template and it will compile it for you and serve it to the browser.
<!-- index.html -->
<link rel="stylesheet" href="app.ts">
You can add a tsconfig.json file at the root of your project and setup your editor in order to control things and to see errors in the console.
node-modules script files
When you build your project, these files are also imported, processed and shipped with your site as part of it.
Only make sure that these files are built to run in the browser.