Merge pull request #44 from zhw2590582/dependabot/npm_and_yarn/cross-env-tw-6.0.0

Update cross-env requirement from ^5.2.1 to ^6.0.0

package.json

@@ -41,7 +41,7 @@
     "chai": "^4.2.0",
     "chalk": "^2.4.2",
     "cpy": "^7.3.0",
-    "cross-env": "^5.2.1",
+    "cross-env": "^6.0.0",
     "cssnano": "^4.1.10",
     "del": "^5.1.0",
     "eslint": "^6.3.0",