--extension <extension>extension, the file extension that we should build
The extension flag is used to tell square which type of build you want to output. As square is primarily build for front-end development it currently supports the following output extensions:
cssCascading Style Sheets.
The extension flag is only used for finding files that either have that
extension or compile code to that extension. For example if you use
css it will compile a build with all the
files that you specified in your bundle.
square ---bundle . --extension css