The pattern-library is installed as a npm-package in the Platform Client. For development, it is not suitable to publish a package for each change, and luckily, there is hack you can do to test the styles locally instead.
Make sure the Pattern-library is built through running gulp build in the terminal
Copy all contents in the "assets" folder
Go to your Platform-client folder
Navigate to node_modules/ushahidi-platform-pattern-library folder
Remove the contents in the "assets" folder
Paste the contents you copied from the assets-folder in the pattern-library
Done! Now you should be able to see the changes in the Platform Client