fix: operating systems

content/post/hacking-on-gitea-actions.md

@@ -251,6 +251,22 @@ Here's how we do it on [gitea.com](http://gitea.com/):
 - To run actions for fork pull requests, approval is required. See [#22803](https://github.com/go-gitea/gitea/pull/22803).
 - If someone registers their own runner for their repository or organization on [gitea.com](http://gitea.com/), we have no objections and will just not use it in our org. However, they should take care to ensure that the runner is not used by other users they do not know.
 
+#### Which operating systems are supported by act runner?
+
+It works well on Linux, macOS, and Windows.
+While other operating systems are theoretically supported, they require further testing.
+
+One thing to note is that if you choose to run jobs directly on the host instead of in job containers, the environmental differences between operating systems may cause unexpected failures.
+
+For example, bash is not available on Windows in most cases, while act tries to use bash to run scripts by default.
+Therefore, you need to specify `powershell` as the default shell in your workflow file, see [defaults.run](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#defaultsrun).
+
+```yaml
+defaults:
+  run:
+    shell: powershell
+```
+
 ## Design
 
 Gitea Actions has multiple parts.