add service worker

package.json

@@ -18,6 +18,7 @@
     "js-cookie": "^2.2.1",
     "line-awesome": "^1.3.0",
     "moment": "^2.29.1",
+    "register-service-worker": "^1.7.1",
     "ua-parser-js": "^0.7.22",
     "vue": "^2.6.12",
     "vue-clipboard2": "^0.3.1",
@@ -29,6 +30,7 @@
   "devDependencies": {
     "@vue/cli-plugin-babel": "~4.5.0",
     "@vue/cli-plugin-eslint": "~4.5.0",
+    "@vue/cli-plugin-pwa": "^4.5.11",
     "@vue/cli-service": "~4.5.0",
     "babel-eslint": "^10.1.0",
     "babel-plugin-component": "^1.1.1",