Migrate babel and postcss configs

.babelrc

@@ -1,18 +0,0 @@
-{
-  "presets": [
-    ["env", {
-      "modules": false,
-      "targets": {
-        "browsers": "> 1%",
-        "uglify": true
-      },
-      "useBuiltIns": true
-    }]
-  ],
-
-  "plugins": [
-    "syntax-dynamic-import",
-    "transform-object-rest-spread",
-    ["transform-class-properties", { "spec": true }]
-  ]
-}

package.json

@@ -4,10 +4,12 @@
   "dependencies": {
     "@rails/ujs": "^6.0.0-alpha",
     "@rails/webpacker": "^4.0.7",
+    "babel-plugin-syntax-dynamic-import": "^6.18.0",
     "bootstrap": "4.3.1",
     "exports-loader": "^0.7.0",
     "jquery": "^3.4.1",
     "popper.js": "^1.15.0",
+    "postcss-preset-env": "^6.7.0",
     "turbolinks": "^5.2.0"
   },
   "version": "0.1.0",

postcss.config.js

@@ -1,7 +1,6 @@
 module.exports = {
   plugins: [
     require('postcss-import'),
-    require('postcss-cssnext'),
     require('postcss-flexbugs-fixes'),
     require('postcss-preset-env')({
       autoprefixer: {

yarn.lock

@@ -1187,6 +1187,11 @@ babel-plugin-macros@^2.5.0:
     cosmiconfig "^5.2.0"
     resolve "^1.10.0"
 
+babel-plugin-syntax-dynamic-import@^6.18.0:
+  version "6.18.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-syntax-dynamic-import/-/babel-plugin-syntax-dynamic-import-6.18.0.tgz#8d6a26229c83745a9982a441051572caa179b1da"
+  integrity sha1-jWomIpyDdFqZgqRBBRVyyqF5sdo=
+
 balanced-match@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
@@ -5309,7 +5314,7 @@ postcss-place@^4.0.1:
     postcss "^7.0.2"
     postcss-values-parser "^2.0.0"
 
-postcss-preset-env@^6.6.0:
+postcss-preset-env@^6.6.0, postcss-preset-env@^6.7.0:
   version "6.7.0"
   resolved "https://registry.yarnpkg.com/postcss-preset-env/-/postcss-preset-env-6.7.0.tgz#c34ddacf8f902383b35ad1e030f178f4cdf118a5"
   integrity sha512-eU4/K5xzSFwUFJ8hTdTQzo2RBLbDVt83QZrAvI07TULOkmyQlnYlpwep+2yIK+K+0KlZO4BvFcleOCCcUtwchg==