docs(advanced): powered by header (#344)

Author: felangel

docs/docs/advanced/powered_by_header.md

@@ -0,0 +1,49 @@
+---
+sidebar_position: 2
+---
+
+# Powered By Header 🔋
+
+By default, all Dart Frog responses include an `X-Powered-By` header:
+
+```
+X-Powered-By: Dart with package:dart_frog
+```
+
+:::info
+The `X-Powered-By` header is supported in `dart_frog >=0.1.2`
+:::
+
+## Changing the `X-Powered-By` Header
+
+The value of this header can be customized by specifying a custom `poweredByHeader` when calling `serve` from a [custom entrypoint](/docs/advanced/custom_entrypoint):
+
+```dart
+import 'dart:io';
+
+import 'package:dart_frog/dart_frog.dart';
+
+Future<HttpServer> run(Handler handler, InternetAddress ip, int port) {
+  return serve(handler, ip, port, poweredByHeader: 'Dart Frog');
+}
+```
+
+With the above changes, all responses would include the following `X-Powered-By` header:
+
+```
+X-Powered-By: Dart Frog
+```
+
+## Removing the `X-Powered-By` Header
+
+The `X-Powered-By` header can be removed by setting the value to `null`:
+
+```dart
+import 'dart:io';
+
+import 'package:dart_frog/dart_frog.dart';
+
+Future<HttpServer> run(Handler handler, InternetAddress ip, int port) {
+  return serve(handler, ip, port, poweredByHeader: null);
+}
+```