feat: add variable to config HomePage width (close #2055)

packages/@vuepress/core/lib/client/style/config.styl

@@ -12,6 +12,7 @@ $badgeErrorColor = #DA5961
 $navbarHeight = 3.6rem
 $sidebarWidth = 20rem
 $contentWidth = 740px
+$homePageWidth = 960px
 
 // responsive breakpoints
 $MQNarrow = 959px

packages/@vuepress/theme-default/components/Home.vue

@@ -86,7 +86,7 @@ export default {
 <style lang="stylus">
 .home
   padding $navbarHeight 2rem 0
-  max-width 960px
+  max-width $homePageWidth
   margin 0px auto
   display block
   .hero

packages/docs/docs/config/README.md

@@ -142,23 +142,35 @@ Specify which pattern of files you want to be resolved.
 
 ### palette.styl
 
-To apply simple color overrides to the styling of the [default preset](https://github.com/vuejs/vuepress/blob/master/packages/@vuepress/core/lib/client/style/config.styl) or define some color variables for using later, you can create a `.vuepress/styles/palette.styl` file.
+To apply simple overrides to the styling of the [default preset](https://github.com/vuejs/vuepress/blob/master/packages/@vuepress/core/lib/client/style/config.styl) or define some variables to use later, you can create a `.vuepress/styles/palette.styl` file.
 
-There are some color variables you can tweak:
+There are some predefined variables you can tweak:
 
 ``` stylus
-// showing default values
+// colors
 $accentColor = #3eaf7c
 $textColor = #2c3e50
 $borderColor = #eaecef
 $codeBgColor = #282c34
+$arrowBgColor = #ccc
 $badgeTipColor = #42b983
 $badgeWarningColor = darken(#ffe564, 35%)
 $badgeErrorColor = #DA5961
+
+// layout
+$navbarHeight = 3.6rem
+$sidebarWidth = 20rem
+$contentWidth = 740px
+$homePageWidth = 960px
+
+// responsive breakpoints
+$MQNarrow = 959px
+$MQMobile = 719px
+$MQMobileNarrow = 419px
 ```
 
 ::: danger Note
-You should ONLY write color variables in this file. Since `palette.styl` will be imported at the end of the root Stylus config file, as a config, several files will use it, so once you wrote styles here, your style would be duplicated by multiple times.
+You should ONLY define variables in this file. Since `palette.styl` will be imported at the end of the root Stylus config file, as a config, several files will use it, so once you wrote styles here, your style would be duplicated by multiple times.
 :::
 
 ### index.styl

packages/docs/docs/zh/config/README.md

@@ -138,23 +138,35 @@ Specify which pattern of files you want to be resolved.
 
 ### palette.styl
 
-如果要对[默认预设](https://github.com/vuejs/vuepress/blob/master/packages/@vuepress/core/lib/client/style/config.styl)的样式应用简单的颜色替换，或者定义一些颜色变量供以后使用，你可以创建一个 `.vuepress/styles/palette.styl` 文件。
+如果要对[默认预设](https://github.com/vuejs/vuepress/blob/master/packages/@vuepress/core/lib/client/style/config.styl)的样式进行简单的替换，或者定义一些变量供以后使用，你可以创建一个 `.vuepress/styles/palette.styl` 文件。
 
-你可以调整一些颜色变量:
+你可以调整的一些变量如下:
 
 ``` stylus
-// 默认值
+// 颜色
 $accentColor = #3eaf7c
 $textColor = #2c3e50
 $borderColor = #eaecef
 $codeBgColor = #282c34
+$arrowBgColor = #ccc
 $badgeTipColor = #42b983
 $badgeWarningColor = darken(#ffe564, 35%)
 $badgeErrorColor = #DA5961
+
+// 布局
+$navbarHeight = 3.6rem
+$sidebarWidth = 20rem
+$contentWidth = 740px
+$homePageWidth = 960px
+
+// 响应式变化点
+$MQNarrow = 959px
+$MQMobile = 719px
+$MQMobileNarrow = 419px
 ```
 
 ::: danger Note
-你应该**只在**这个文件中写入颜色变量。因为 `palette.styl` 将在根的 stylus 配置文件的末尾引入，作为配置，它将被多个文件使用，所以一旦你在这里写了样式，你的样式就会被多次复制。
+你应该**只在**这个文件中定义变量。因为 `palette.styl` 将在根的 stylus 配置文件的末尾引入，作为配置，它将被多个文件使用，所以一旦你在这里写了样式，你的样式就会被多次复制。
 :::
 
 ### index.styl