The problem with this is it won't work inside // comments!
lessc allows for --global-var which could be used for build number.
You can see some problems with this method (might not allow . characters).
// current
npx lessc --clean-css=\"--s1 --advanced\" source/style/main.less ./build/style/print-first.css
// proposed addition
--global-var="cssVersion=$(npm pkg get version)"
You can see some problems with this method (might not allow
.characters).