docs: Add instructions for setting up `fish_indent` for fish (#38414)

Justin Su created

Release Notes:

- N/A

Change summary

docs/src/languages/fish.md | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

Detailed changes

docs/src/languages/fish.md 🔗

@@ -4,3 +4,28 @@ Fish language support in Zed is provided by the community-maintained [Fish exten
 Report issues to: [https://github.com/hasit/zed-fish/issues](https://github.com/hasit/zed-fish/issues)
 
 - Tree-sitter: [ram02z/tree-sitter-fish](https://github.com/ram02z/tree-sitter-fish)
+
+### Formatting
+
+Zed supports auto-formatting fish code using external tools like [`fish_indent`](https://fishshell.com/docs/current/cmds/fish_indent.html), which is included with fish.
+
+1. Ensure `fish_indent` is available in your path and check the version:
+
+```sh
+which fish_indent
+fish_indent --version
+```
+
+2. Configure Zed to automatically format fish code with `fish_indent`:
+
+```json
+  "languages": {
+    "Fish": {
+      "formatter": {
+        "external": {
+          "command": "fish_indent"
+        }
+      }
+    }
+  },
+```