There is no special plugin for JetBrains' IDEs.
Instead, you can use CSScomb as an external tool:

1. Install CSScomb: npm install csscomb
2. Go to Preferences > External Tools (or press ⌘, on Mac)
3. Click on Add icon (or press ⌘N on Mac)
4. Fill the form with following info:
   – Name: CSScomb
   – Program: path_to_installed_csscomb/bin/csscomb
   – Parameters: $FilePath$
   – Working directory: $FileDir$

All checkboxes in the form are optional, you can check whichever you want.
CSScomb will be available then in all menus you select.

You can place .csscomb.json file in the project's directory, or your HOME directory, or anywhere else.
See docs for info.