docs: add docs about "versions"

website/docs/options.md

@@ -90,6 +90,22 @@ The text for *edit link*.
 
 Centering contents.
 
+## versions
+
+- Type: `Versions`
+
+When specified, Docute will show a version selector at the sidebar.
+
+```ts
+interface Versions {
+  // The version number, like `v1`
+  [version: string]: {
+    // The link to this version of docs
+    link: string
+  }
+}
+```
+
 ## overrides
 
 - Type: `{[path: string]: LocaleOptions}`

website/docs/zh/options.md

@@ -91,6 +91,22 @@ https://github.com/USER/REPO/blob/master/docs
 
 内容居中。
 
+## versions
+
+- 类型: `Versions`
+
+设置此项之后, Docute 会在侧边栏显示一个版本选择器。
+
+```ts
+interface Versions {
+  // 版本号, 比如 `v1`
+  [version: string]: {
+    // 指向相关文档的链接
+    link: string
+  }
+}
+```
+
 ## overrides
 
 - 类型：`{[path: string]: LocaleOptions}`

website/index.js

@@ -21,7 +21,7 @@ new Docute({
     }
   ],
   versions: {
-    v4: {
+    'v4 (Latest)': {
       link: '/'
     },
     v3: {