⬆️ Upgrade to Vue CLI 4 (#120)

* Upgrade to Vue CLI 4

https://cli.vuejs.org/migrating-from-v3

* 🔥 Remove package-lock.json that varies by system

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

{{cookiecutter.project_slug}}/frontend/package.json

@@ -5,12 +5,13 @@
   "scripts": {
     "serve": "vue-cli-service serve",
     "build": "vue-cli-service build",
-    "lint": "vue-cli-service lint",
-    "test:unit": "vue-cli-service test:unit"
+    "test:unit": "vue-cli-service test:unit",
+    "lint": "vue-cli-service lint"
   },
   "dependencies": {
     "@babel/polyfill": "^7.2.5",
     "axios": "^0.18.0",
+    "core-js": "^3.4.3",
     "register-service-worker": "^1.0.0",
     "typesafe-vuex": "^3.1.1",
     "vee-validate": "^2.1.7",
@@ -23,16 +24,16 @@
   },
   "devDependencies": {
     "@types/jest": "^23.3.13",
-    "@vue/cli-plugin-babel": "^3.3.0",
-    "@vue/cli-plugin-pwa": "^3.3.0",
-    "@vue/cli-plugin-typescript": "^3.3.0",
-    "@vue/cli-plugin-unit-jest": "^3.5.0",
-    "@vue/cli-service": "^3.3.1",
+    "@vue/cli-plugin-babel": "^4.1.1",
+    "@vue/cli-plugin-pwa": "^4.1.1",
+    "@vue/cli-plugin-typescript": "^4.1.1",
+    "@vue/cli-plugin-unit-jest": "^4.1.1",
+    "@vue/cli-service": "^4.1.1",
     "@vue/test-utils": "^1.0.0-beta.28",
     "babel-core": "7.0.0-bridge.0",
     "ts-jest": "^23.10.5",
     "typescript": "^3.2.4",
-    "vue-cli-plugin-vuetify": "^0.2.1",
+    "vue-cli-plugin-vuetify": "^2.0.2",
     "vue-template-compiler": "^2.5.22"
   },
   "postcss": {