chore: bump postcss version

See postcss/postcss#1574 (comment)

Author: haoqunjiang

Diff for: package.json

@@ -60,7 +60,7 @@
     "hash-sum": "^1.0.2",
     "lru-cache": "^4.1.2",
     "merge-source-map": "^1.1.0",
-    "postcss": "^7.0.14",
+    "postcss": "^7.0.36",
     "postcss-selector-parser": "^6.0.2",
     "source-map": "~0.6.1",
     "vue-template-es2015-compiler": "^1.9.0"