chore: add actionlint guide

kagankan · kagankan · commit c586cf3ca315 · 2024-08-26T03:41:34.000+09:00
diff --git a/README.md b/README.md
@@ -16,6 +16,9 @@ To start a development server:
 yarn run dev
 ```
 
+If you want to modify GitHub workflow, you need to install `actionlint`.
+See [Installation document](https://github.com/rhysd/actionlint/blob/main/docs/install.md).
+
 ## Thanks
 
 This playground is inspired by:
