Add PWA support.

package.json

@@ -15,17 +15,19 @@
         "core-js": "^3.7.0",
         "css-loader": "^5.0.1",
         "less": "^3.12.2",
-        "less-loader": "^7.0.2",
+        "less-loader": "^7.1.0",
+        "register-service-worker": "^1.7.1",
         "uikit": "^3.5.9",
         "video.js": "^7.10.2",
         "videojs-contrib-quality-levels": "^2.0.9",
         "videojs-hotkeys": "^0.2.27",
         "vue": "^3.0.0",
-        "vue-router": "^4.0.0-rc.2"
+        "vue-router": "^4.0.0-rc.3"
     },
     "devDependencies": {
         "@vue/cli-plugin-babel": "~4.5.0",
         "@vue/cli-plugin-eslint": "~4.5.0",
+        "@vue/cli-plugin-pwa": "^4.5.8",
         "@vue/cli-service": "~4.5.0",
         "@vue/compiler-sfc": "^3.0.0",
         "babel-eslint": "^10.1.0",
@@ -51,4 +53,4 @@
         "last 2 versions",
         "not dead"
     ]
-}
+}