docs: Set the docs favicon to ⚓ (#895)

docs/src/.vuepress/config.js

@@ -17,6 +17,7 @@ module.exports = {
    * ref：https://v1.vuepress.vuejs.org/config/#head
    */
   head: [
+    ["link", { rel: "icon", href: "data:image/svg+xml,<svg xmlns=%22http://www.w3.org/2000/svg%22 viewBox=%220 0 100 100%22><text y=%22.9em%22 font-size=%2290%22>⚓ </text></svg>"}],
     ["meta", { name: "theme-color", content: "#3eaf7c" }],
     ["meta", { name: "apple-mobile-web-app-capable", content: "yes" }],
     [