move cssnano to devDependencies

package.json

@@ -53,6 +53,7 @@
     "babel-jest": "^27.0.2",
     "clean-css": "^5.1.2",
     "cross-env": "^7.0.3",
+    "cssnano": "^5.0.5",
     "eslint": "^7.28.0",
     "eslint-config-prettier": "^8.3.0",
     "eslint-plugin-prettier": "^3.4.0",
@@ -74,7 +75,7 @@
     "chalk": "^4.1.1",
     "chokidar": "^3.5.1",
     "color": "^3.1.3",
-    "cssnano": "^5.0.5",
+    "cosmiconfig": "^7.0.0",
     "detective": "^5.2.0",
     "didyoumean": "^1.2.1",
     "dlv": "^1.1.3",

package.postcss7.json

@@ -1,4 +1,7 @@
 {
+  "devDependencies": {
+    "cssnano": "^4"
+  },
   "dependencies": {
     "@fullhuman/postcss-purgecss": "^3.1.3",
     "autoprefixer": "^9",