docs: add api navbar link

Author: PeachScript

docs/.vuepress/config.js

@@ -21,6 +21,10 @@ module.exports = {
             text: 'Guide',
             link: '/guide/',
           },
+          {
+            text: 'API',
+            link: '/api/',
+          },
         ],
         sidebar: {
           '/guide/': [
@@ -51,6 +55,10 @@ module.exports = {
             text: '指南',
             link: '/zh/guide/',
           },
+          {
+            text: 'API',
+            link: '/zh/api/',
+          },
         ],
         sidebar: {
           '/zh/guide/': [