docs: add configuration example (#86)

* Add configuration example

* Update README.md

Co-authored-by: pooya parsa <pyapar@gmail.com>

README.md

@@ -49,6 +49,32 @@ You can either use `unbuild` key in `package.json` or `build.config.{js,ts,json}
 
 See options [here](./src/types.ts).
 
+Example:
+
+```ts
+import { defineBuildConfig } from 'unbuild'
+
+export default defineBuildConfig({
+    // If entries is not provided, will be automatically inferred from package.json 
+    entries: [
+        // default
+        './src/index',
+        // mkdist builder transpiles file-to-file keeping original sources structure
+        {
+            builder: 'mkdist',
+            input: './src/package/components/',
+            outDir: './build/components'
+        },
+    ],
+
+    // Change outDir, default is 'dist'
+    outDir: 'build',
+
+    // Generates .d.ts declaration file
+    declaration: true,
+})
+```
+
 ## 💻 Development
 
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