docs: add global-computed

Author: ulivz

packages/docs/docs/miscellaneous/global-computed.md

@@ -0,0 +1,83 @@
+---
+sidebar: auto
+---
+
+# Global Computed
+
+In VuePress, some core [computed](https://vuejs.org/v2/guide/computed.html#Computed-Properties) properties are built in for use by [default theme](../theme/default-theme-config.md) or custom themes.
+
+## $site
+
+This is the `$site` value of the website you see now:
+
+``` json
+{
+  "title": "VuePress",
+  "description": "Vue 驱动的静态网站生成器",
+  "base": "/",
+  "pages": [
+    {
+      "lastUpdated": 1524027677000,
+      "path": "/",
+      "title": "VuePress",
+      "frontmatter": {}
+    },
+    ...
+  ]
+}
+```
+
+## $page
+
+This is the `$page` value of the page you see now:
+
+``` json
+{
+  "title": "Global Computed",
+  "frontmatter": {},
+  "regularPath": "/miscellaneous/global-computed.html",
+  "key": "v-d4cbeb69eff3d",
+  "path": "/miscellaneous/global-computed.html",
+  "headers": [
+    {
+      "level": 2,
+      "title": "$site",
+      "slug": "site"
+    },
+    {
+      "level": 2,
+      "title": "$page",
+      "slug": "$page"
+    },
+    ...
+  ]
+}
+```
+
+## $lang
+
+The language of the current page. default value is `en-US`.
+
+**Also see:**
+
+- [Internationalization](../guide/i18n.md)
+
+## $localePath
+
+The locale path prefix for the current page, the default value is `/`.
+
+**Also see:**
+
+- [Internationalization](../guide/i18n.md)
+
+## $title
+
+Value of the `<title>` label used for the current page.
+
+## $description
+
+The `content` value of the `<meta name= "description" content= "...">` for the current page.
+
+## $themeConfig
+
+i.e. `siteConfig.themeConfig`。

packages/docs/docs/zh/miscellaneous/global-computed.md

@@ -0,0 +1,85 @@
+---
+sidebar: auto
+---
+
+# 全局计算属性
+
+在 VuePress 中，内置了一些核心的[计算属性](https://cn.vuejs.org/v2/guide/computed.html#%E8%AE%A1%E7%AE%97%E5%B1%9E%E6%80%A7)，以供[默认主题](../theme/default-theme-config.md) 或自定义主题使用。
+
+## $site
+
+这是你现在看到的这个网站的 `$site` 的值：
+
+``` json
+{
+  "title": "VuePress",
+  "description": "Vue 驱动的静态网站生成器",
+  "base": "/",
+  "pages": [
+    {
+      "lastUpdated": 1524027677000,
+      "path": "/",
+      "title": "VuePress",
+      "frontmatter": {}
+    },
+    ...
+  ]
+}
+```
+
+## $page
+
+这是你现在看到的这个页面的 `$page` 的值：
+
+``` json
+{
+  "title": "Global Computed",
+  "frontmatter": {
+    "sidebar": "auto"
+  },
+  "regularPath": "/zh/miscellaneous/global-computed.html",
+  "key": "v-bc9a3e3f9692d",
+  "path": "/zh/miscellaneous/global-computed.html",
+  "headers": [
+    {
+      "level": 2,
+      "title": "$site",
+      "slug": "site"
+    },
+    {
+      "level": 2,
+      "title": "$page",
+      "slug": "page"
+    },
+    ...
+  ]
+}
+```
+
+## $lang
+
+当前页面的语言，默认值为 `en-US`。
+
+**参考:**
+
+- [多语言支持](../guide/i18n.md)
+
+## $localePath
+
+当前页面的 locale 路径前缀，默认值为 `/`，当前页面为 `/zh/`。
+
+**参考:**
+
+- [多语言支持](../guide/i18n.md)
+
+## $title
+
+用于当前页面的 `<title>` 标签的值。
+
+## $description
+
+用于当前页面的 `<meta name="description" content="...">` 的 `content` 值。
+
+## $themeConfig
+
+即 `siteConfig.themeConfig`。