refactor(theming): split up styles

package.json

@@ -10,7 +10,7 @@
     "url": "https://github.com/wbkd/react-flow.git"
   },
   "scripts": {
-    "build": "rollup -c --environment NODE_ENV:production && move-file dist/nocss/style.css dist/style.css",
+    "build": "rollup -c --environment NODE_ENV:production && postcss src/*.css --dir dist",
     "start": "rollup -w -c",
     "start:examples": "rollup -c rollup.examples.js -w",
     "build:examples": "rollup -c rollup.examples.js --environment NODE_ENV:production",
@@ -58,8 +58,8 @@
     "cypress": "^6.3.0",
     "dagre": "^0.8.5",
     "localforage": "^1.9.0",
-    "move-file-cli": "^2.0.0",
     "postcss": "^8.2.4",
+    "postcss-cli": "^8.3.1",
     "postcss-nested": "^5.0.3",
     "prettier": "2.2.1",
     "prop-types": "^15.7.2",