Add polymer decorators and update @polymer/ libraries versions

Without updating @polymer/ libraries, yarn installs 2 versions of
@polymer/polymer library, which leads to type errors in typescript

Change-Id: Ib581436c03c8e6b674820bb33b14fb085e986548
diff --git a/polygerrit-ui/app/package.json b/polygerrit-ui/app/package.json
index 32560ff..d6e94fc 100644
--- a/polygerrit-ui/app/package.json
+++ b/polygerrit-ui/app/package.json
@@ -3,31 +3,32 @@
   "description": "Gerrit Code Review - Polygerrit dependencies",
   "browser": true,
   "dependencies": {
+    "@polymer/decorators": "^3.0.0",
     "@polymer/font-roboto-local": "^3.0.2",
     "@polymer/iron-a11y-keys-behavior": "^3.0.1",
-    "@polymer/iron-autogrow-textarea": "^3.0.1",
+    "@polymer/iron-autogrow-textarea": "^3.0.3",
     "@polymer/iron-dropdown": "^3.0.1",
-    "@polymer/iron-fit-behavior": "^3.0.1",
+    "@polymer/iron-fit-behavior": "^3.0.2",
     "@polymer/iron-icon": "^3.0.1",
     "@polymer/iron-iconset-svg": "^3.0.1",
     "@polymer/iron-input": "^3.0.1",
-    "@polymer/iron-overlay-behavior": "^3.0.2",
+    "@polymer/iron-overlay-behavior": "^3.0.3",
     "@polymer/iron-selector": "^3.0.1",
     "@polymer/paper-button": "^3.0.1",
     "@polymer/paper-dialog": "^3.0.1",
     "@polymer/paper-dialog-behavior": "^3.0.1",
     "@polymer/paper-dialog-scrollable": "^3.0.1",
-    "@polymer/paper-input": "^3.0.2",
+    "@polymer/paper-input": "^3.2.1",
     "@polymer/paper-item": "^3.0.1",
     "@polymer/paper-listbox": "^3.0.1",
     "@polymer/paper-tabs": "^3.1.0",
     "@polymer/paper-toggle-button": "^3.0.1",
-    "@polymer/polymer": "^3.3.0",
+    "@polymer/polymer": "^3.4.1",
     "@webcomponents/shadycss": "^1.9.2",
     "@webcomponents/webcomponentsjs": "^1.3.3",
+    "ba-linkify": "file:../../lib/ba-linkify/src/",
     "page": "^1.11.5",
     "polymer-bridges": "file:../../polymer-bridges/",
-    "ba-linkify": "file:../../lib/ba-linkify/src/",
     "polymer-resin": "^2.0.1"
   },
   "license": "Apache-2.0",