docs: update css vars

Author: anlyyao

src/navbar/README.en-US.md

@@ -53,7 +53,7 @@ Name | Default Value | Description
 --td-navbar-capsule-height | 32px | - 
 --td-navbar-capsule-width | 88px | - 
 --td-navbar-center-left | @navbar-right | - 
---td-navbar-center-width | --td-navbar-center-width | - 
+--td-navbar-center-width | 187px | - 
 --td-navbar-color | @text-color-primary | - 
 --td-navbar-height | 48px | - 
 --td-navbar-left-arrow-size | 24px | - 

src/navbar/README.md

@@ -102,7 +102,7 @@ t-class-title | 标题样式类
 --td-navbar-capsule-height | 32px | - 
 --td-navbar-capsule-width | 88px | - 
 --td-navbar-center-left | @navbar-right | - 
---td-navbar-center-width | --td-navbar-center-width | - 
+--td-navbar-center-width | 187px | - 
 --td-navbar-color | @text-color-primary | - 
 --td-navbar-height | 48px | - 
 --td-navbar-left-arrow-size | 24px | - 

src/qrcode/README.en-US.md

@@ -24,3 +24,11 @@ value | String | - | scanned text | N
 name | params | description
 -- | -- | --
 refresh | \- | Click the "Click to refresh" callback
+
+
+### CSS Variables
+
+The component provides the following CSS variables, which can be used to customize styles.
+Name | Default Value | Description 
+-- | -- | --
+--td-font-size-title-small | --td-font-size-title-small | - 

src/qrcode/README.md

@@ -101,11 +101,7 @@ t-class | 根节点样式类
 
 ### CSS Variables
 
-
 组件提供了下列 CSS 变量，可用于自定义样式。
-
-名称 | 默认值 | 描述
+名称 | 默认值 | 描述 
 -- | -- | --
---td-qrcode-border-color | #dcdcdc | -
---td-qrcode-border-width | 1px | -
---td-qrcode-border-radius | 6px | -
+--td-font-size-title-small | --td-font-size-title-small | -