⚒ upgrade codecov (#55)

Author: mysticatea

package.json

@@ -21,7 +21,7 @@
     "@typescript-eslint/parser": "^4.8.2",
     "@vuepress/plugin-pwa": "^1.2.0",
     "acorn": "^7.1.0",
-    "codecov": "3.7.0",
+    "codecov": "^3.8.1",
     "eslint": "^7.10.0",
     "eslint4b": "^7.10.0",
     "espree": "^7.0.0",