Build bundled web assets instead of serving source files

I would like to consider serving bundled web resources (JavaScript, CSS, maybe even HTML) built from source files, instead of serving the source files directly to clients. Some of the tooling involved could be:

* https://babeljs.io/ for JavaScript backward-compatibility
* https://github.com/postcss/autoprefixer for CSS backward compatibility
* A bundler and optimizer (there are many options) to combine well-organized source into small optimized output.

I'd want to make sure that any tools involved include some way to continue debugging with the original code, whether that's through source maps, or just having a developer mode that uses the original source directly.