CssSyntaxError @fullcalendar/common/main.css Unknown word

I'm using Ember 3.19 and ember-auto-import@^1.5.3 with webpack config to build @fullcalendar/core@^5.5.0 as a module into my Ember app.

I run into this error during build, not certain what the issue is since the line causing the syntax error cannot be found in the package at all.

ERROR in ./node_modules/@fullcalendar/common/main.css
Module build failed (from ./node_modules/css-loader/dist/cjs.js):
CssSyntaxError

(1:1) ./node_modules/@fullcalendar/common/main.css Unknown word

> 1 | // Imports
    | ^
  2 | import ___CSS_LOADER_API_IMPORT___ from "../../css-loader/dist/runtime/api.js";
  3 | var ___CSS_LOADER_EXPORT___ = ___CSS_LOADER_API_IMPORT___(function(i){return i[1]});

 @ ./node_modules/@fullcalendar/common/main.js 6:0-20
 @ ./node_modules/@fullcalendar/core/main.js
 @ /tmp/broccoli-6893zcFAzhUCZAyl/cache-1309-bundler/staging/app.js
 @ multi /tmp/broccoli-6893zcFAzhUCZAyl/cache-1309-bundler/staging/l.js /tmp/broccoli

Below is my webpack config

webpack: {
    module: {
        rules: [ 
            { 
                test: /\.css$/, 
                include: [ path.resolve(__dirname, 'node_modules/@fullcalendar') ],
                use: ['css-loader'] 
            } 
        ]
    }
}