docs: webpack

Author: Guillaume Chau

docs/.vuepress/config.js

@@ -39,6 +39,7 @@ module.exports = {
             '',
             'configuration',
             'directives',
+            'webpack',
           ],
         },
       },

docs/guide/webpack.md

@@ -0,0 +1,33 @@
+# Webpack configuration
+
+In `api.chainWebpack` and `api.configureWebpack`, you have access to some environment variables:
+
+- **`process.env.VUE_CLI_SSR_TARGET`**: Either `'client'` or `'server'`
+
+- **`process.env.VUE_CLI_MODE`**: Vue CLI mode
+
+Examples:
+
+```js
+api.chainWebpack(config => {
+  if (process.env.VUE_CLI_SSR_TARGET === 'client') {
+    // Client-only config
+  } else {
+    // SSR-only config
+  }
+})
+```
+
+```js
+api.configureWebpack(config => {
+  if (process.env.VUE_CLI_SSR_TARGET === 'client') {
+    return {
+      // Client-only config
+    }
+  } else {
+    return {
+      // SSR-only config
+    }
+  }
+})
+```