fix: solve postcss-values-parser Syntax Error problem

When using Rollup for balloon.css, `calc(var(--balloon-move) * -1))` will become like this `calc(var(--balloon-move)*-1))`. The space was removed.

This will lead to postcss-values-parser Syntax Error, such as webpacker of Ruby on Rails.

Ref https://github.com/postcss/postcss-custom-properties/issues/161#issuecomment-479025016

scripts/creatRollupConfig.js

@@ -47,7 +47,12 @@ module.exports = function creatRollupConfig(projectPath) {
                 plugins: [
                     autoprefixer(),
                     cssnano({
-                        preset: 'default',
+                        preset: [
+                            'default',
+                            {
+                                calc: false
+                            }
+                        ],
                     }),
                 ],
                 sourceMap: isProd ? false : true,