The new extraEntries configuration has been correctly defined under the config.clientlibs object. However, it is currently being accessed as config.postcss.extraEntries in the codebase. This leads to incorrect behavior or a misinterpretation of the configuration source.

Proposed solution:
Update the following files to read from config.clientlibs.extraEntries instead of config.postcss.extraEntries:

tasks/clientlibs.js
utils/renderClientLibs.js

This will ensure consistency with the intended configuration structure and prevent potential confusion or misconfiguration in the future.