Coding a small file bundler for HTML/JS/CSS

So my project has a lot of small "widget" like components with their own css and js. What I need is a sort of automatism to "bundle" up the css and js of all the components into a single file with a press of a button.(or cmd expression)

Something like this: "bundleMeFiles.exe -header -footer -widget1" or if all: "bundleMeFiles.exe -all"

I know there are tools and a lot of stuff that does that in a great scale but I'm also a DIY guy so I like doing my own stuff because it makes me improve.

My first guess is Powershell or even Java to build a fancy UI but any tips would be welcome.

Thanks in advance