feat: use core-js 3 (Kocal#410)

Author: Kocal

template/.babelrc

@@ -5,6 +5,7 @@
   "presets": [
     ["@babel/preset-env", {
       "useBuiltIns": "usage",
+      "corejs": 3,
       "targets": {
         // https://jamie.build/last-2-versions
         "browsers": ["> 0.25%", "not ie 11", "not op_mini all"]

template/package.json

@@ -77,7 +77,7 @@
     "@babel/preset-env": "^7.1.0",
     "babel-loader": "^8.0.2",
     "copy-webpack-plugin": "^4.5.3",
-    "core-js": "^2.6.5",
+    "core-js": "^3.0.1",
     "cross-env": "^5.2.0",
     "css-loader": "^0.28.11",
     "ejs": "^2.6.1",