[Doc] support pick document version

package.json

@@ -71,7 +71,7 @@
     "@babel/preset-env": "^7.4.4",
     "@babel/preset-typescript": "^7.3.3",
     "@types/jest": "^24.0.13",
-    "@vant/doc": "^2.1.0",
+    "@vant/doc": "^2.2.0",
     "@vant/eslint-config": "^1.1.2",
     "@vant/markdown-loader": "^2.0.0",
     "@vue/babel-preset-jsx": "^1.0.0",
@@ -117,9 +117,9 @@
     "vue-server-renderer": "^2.6.10",
     "vue-template-compiler": "2.6.10",
     "vue-template-es2015-compiler": "^1.9.1",
-    "webpack": "^4.32.0",
+    "webpack": "4.31.0",
     "webpack-cli": "^3.3.2",
-    "webpack-dev-server": "^3.4.1"
+    "webpack-dev-server": "3.3.1"
   },
   "vetur": {
     "tags": "vetur/tags.json",