feat($theme-default): use plugin-smooth-scroll (close vuejs#567)

Author: meteorlxy

packages/@vuepress/theme-default/index.js

@@ -41,6 +41,7 @@ module.exports = (options, ctx) => ({
         '/': 'WARNING',
         '/zh/': '警告'
       }
-    }]
+    }],
+    'smooth-scroll'
   ]
 })

packages/@vuepress/theme-default/package.json

@@ -37,6 +37,7 @@
     "lodash": "^4.17.15",
     "stylus": "^0.54.5",
     "stylus-loader": "^3.0.2",
-    "vuepress-plugin-container": "^2.0.0"
+    "vuepress-plugin-container": "^2.0.0",
+    "vuepress-plugin-smooth-scroll": "^0.0.3"
   }
 }

yarn.lock

@@ -10461,6 +10461,11 @@ [email protected]:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/smart-buffer/-/smart-buffer-4.0.2.tgz#5207858c3815cc69110703c6b94e46c15634395d"
 
+smoothscroll-polyfill@^0.4.3:
+  version "0.4.4"
+  resolved "https://registry.yarnpkg.com/smoothscroll-polyfill/-/smoothscroll-polyfill-0.4.4.tgz#3a259131dc6930e6ca80003e1cb03b603b69abf8"
+  integrity sha512-TK5ZA9U5RqCwMpfoMq/l1mrH0JAR7y7KRvOBx0n2869aLxch+gT9GhN3yUfjiw+d/DiF1mKo14+hd62JyMmoBg==
+
 snapdragon-node@^2.0.1:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/snapdragon-node/-/snapdragon-node-2.1.1.tgz#6c175f86ff14bdb0724563e8f3c1b021a286853b"
@@ -11990,6 +11995,13 @@ vuepress-plugin-flowchart@^1.4.2:
   dependencies:
     flowchart.js "^1.11.3"
 
+vuepress-plugin-smooth-scroll@^0.0.3:
+  version "0.0.3"
+  resolved "https://registry.yarnpkg.com/vuepress-plugin-smooth-scroll/-/vuepress-plugin-smooth-scroll-0.0.3.tgz#6eff2d4c186cca917cc9f7df2b0af7de7c8c6438"
+  integrity sha512-qsQkDftLVFLe8BiviIHaLV0Ea38YLZKKonDGsNQy1IE0wllFpFIEldWD8frWZtDFdx6b/O3KDMgVQ0qp5NjJCg==
+  dependencies:
+    smoothscroll-polyfill "^0.4.3"
+
 w3c-hr-time@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/w3c-hr-time/-/w3c-hr-time-1.0.1.tgz#82ac2bff63d950ea9e3189a58a65625fedf19045"