update custom-theme docs

examples/docs/en-US/custom-theme.md

@@ -110,12 +110,15 @@ Vue.use(ElementUI)
 If you are using `babel-plugin-component` for on-demand import, just modify `.babelrc` and specify `styleLibraryName` to the path where your custom theme is located relative to `.babelrc`. Note that `~` is required:
 ```json
 {
-  "plugins": [["component", [
-    {
-      "libraryName": "element-ui",
-      "styleLibraryName": "~theme"
-    }
-  ]]]
+  "plugins": [
+    [
+      "component",
+      {
+        "libraryName": "element-ui",
+        "styleLibraryName": "~theme"
+      }
+    ]
+  ]
 }
 ```
 

examples/docs/es/custom-theme.md

@@ -110,12 +110,15 @@ Vue.use(ElementUI)
 Si esta utilizando `babel-plugin-component` para importar bajo demanda, solo debe modificar el archivo `.babelrc` y especificar en la propiedad `styleLibraryName` la ruta en donde se encuentra localizado su tema personalizado relativo a `.babelrc`. **Nota** el carácter `~` es obligatorio:
 ```json
 {
-  "plugins": [["component", [
-    {
-      "libraryName": "element-ui",
-      "styleLibraryName": "~theme"
-    }
-  ]]]
+  "plugins": [
+    [
+      "component",
+      {
+        "libraryName": "element-ui",
+        "styleLibraryName": "~theme"
+      }
+    ]
+  ]
 }
 ```
 

examples/docs/zh-CN/custom-theme.md

@@ -109,12 +109,15 @@ Vue.use(ElementUI)
 如果是搭配 `babel-plugin-component` 一起使用，只需要修改 `.babelrc` 的配置，指定 `styleLibraryName` 路径为自定义主题相对于 `.babelrc` 的路径，注意要加 `~`。
 ```json
 {
-  "plugins": [["component", [
-    {
-      "libraryName": "element-ui",
-      "styleLibraryName": "~theme"
-    }
-  ]]]
+  "plugins": [
+    [
+      "component",
+      {
+        "libraryName": "element-ui",
+        "styleLibraryName": "~theme"
+      }
+    ]
+  ]
 }
 ```