added resources/sass/tool.scss to webpack.mix.js to avoid file not found errors for the nova tool css file

Author: bjrnblm

dist/css/tool.css

@@ -1,3 +1,4 @@
-let mix = require('laravel-mix')
+let mix = require('laravel-mix');
 
 mix.js('resources/js/tool.js', 'dist/js');
+mix.sass('resources/sass/tool.scss', 'dist/css');