You can minify JS files manually using https://closure-compiler.appspot.com/
Click Reset, then paste the code on the left, then click Compile. Then you can download the code on the right.
As Pupi said you should do this with the .js files themselves, not PHP code. There are also online minifiers for CSS, they’re easy to find.
I’ve considered adding minification to Q2A itself, but it adds a bit of complexity from a development perspective. If people make changes they’d also have to minify the files manually to test. In general it’s better to not have minified files in source control which would solve that problem, but that means adding an additional build process when people install Q2A.
I should also add, minification does not make a huge amount of difference to download time when the files are gzipped.