docs: display all less variables (#7604)

src/toast/README.md

@@ -168,3 +168,25 @@ Toast.resetDefaultOptions('loading');
 | onClose | Callback function after close | _Function_ | - |
 | transition | Transition, equivalent to `name` prop of [transtion](https://vuejs.org/v2/api/#transition) | _string_ | `van-fade` |
 | getContainer | Return the mount node for Toast | _string \| () => Element_ | `body` |
+
+### Less Variables
+
+How to use: [Custom Theme](#/en-US/theme).
+
+| Name                            | Default Value             | Description |
+| ------------------------------- | ------------------------- | ----------- |
+| @toast-max-width                | `70%`                     | -           |
+| @toast-font-size                | `@font-size-md`           | -           |
+| @toast-text-color               | `@white`                  | -           |
+| @toast-loading-icon-color       | `@white`                  | -           |
+| @toast-line-height              | `@line-height-md`         | -           |
+| @toast-border-radius            | `@border-radius-lg`       | -           |
+| @toast-background-color         | `fade(@black, 70%)`       | -           |
+| @toast-icon-size                | `36px`                    | -           |
+| @toast-text-min-width           | `96px`                    | -           |
+| @toast-text-padding             | `@padding-xs @padding-sm` | -           |
+| @toast-default-padding          | `@padding-md`             | -           |
+| @toast-default-width            | `88px`                    | -           |
+| @toast-default-min-height       | `88px`                    | -           |
+| @toast-position-top-distance    | `20%`                     | -           |
+| @toast-position-bottom-distance | `20%`                     | -           |