add favicon

Author: cjpearson

docs/.vuepress/config.js

@@ -22,6 +22,9 @@ module.exports = {
     }
   },
   serviceWorker: true,
+  head: [
+    ['link', { rel: 'icon', href: '/favicon.png' }]
+  ],
   theme: 'vue',
   themeConfig: {
     algolia: {