build: update melos files

index_generator.yaml

@@ -0,0 +1,11 @@
+index_generator:
+  exclude:
+    - '**.g.dart'
+  # Define the paths of the folders in which to generate the index files
+  indexes:
+    - path: lib
+      disclaimer: false
+      comments: |
+        Copyright 2023 The dart-action Authors. All rights reserved.
+        Use of this source code is governed by a Apache 2.0 license that can be
+        found in the LICENSE file.

melos.yaml

@@ -15,7 +15,12 @@ scripts:
     exec: dart format --set-exit-if-changed .
   cp_files:
     exec: cp ../../LICENSE . && cp ../../.markdownlint.jsonc .
-
+  index_file:
+    exec: |
+      cp ../../index_generator.yaml .
+      dart pub add dev:index_generator:^3.4.0
+      dart pub get
+      dart run index_generator:index_generator
 sdkPath: auto
 
 command: