docs: fix nprogress title issue

Author: meteorlxy

docs/reference/plugin/nprogress.md

@@ -1,4 +1,12 @@
-# nprogress
+---
+title: nprogress
+---
+
+<!-- `# nprogress` will be rendered as `<h1 id="nprogress">`, and the id will conflict with the nprogress bar (stupid) -->
+
+<!-- so we add a 'plugin' suffix in the h1 title, and use title frontmatter to set the page title -->
+
+# nprogress Plugin
 
 > @vuepress/plugin-nprogress
 

docs/zh/reference/plugin/nprogress.md

@@ -1,4 +1,12 @@
-# nprogress
+---
+title: nprogress
+---
+
+<!-- `# nprogress` 会被渲染成 `<h1 id="nprogress">` ，导致 id 和 nprogress 进度条冲突 （有点蠢） -->
+
+<!-- 所以我们在 h1 标题后添加一个 '插件' 后缀，然后通过 title frontmatter 来设置页面标题 -->
+
+# nprogress 插件
 
 > @vuepress/plugin-nprogress