docs: change doc

Author: Meet-student

website/docs/en/config/devtool.mdx

@@ -14,7 +14,7 @@ Use the [SourceMapDevToolPlugin](/plugins/webpack/source-map-dev-tool-plugin) or
 type Devtool = 'string' | false;
 ```
 
-- **Default:** `eval`
+- **Default:** production mode is `source-map`, development mode is `cheap-module-source-map`
 
 ## Configuration guide
 

website/docs/zh/config/devtool.mdx

@@ -14,7 +14,7 @@ import WebpackLicense from '@components/WebpackLicense';
 type Devtool = 'string' | false;
 ```
 
-- **默认值：** `eval`
+- **默认值：** production 模式 为 `source-map`, development 模式 为 `cheap-module-source-map`
 
 ## 决策指南