docs: Add theme ID suffix recommendation (#48679)

José Duarte and Finn Evers created 

Added note about suffixing theme IDs with '-theme' for clarity.

As discussed in
https://github.com/zed-industries/extensions/pull/4693#pullrequestreview-3751636461

- [ ] ~Tests or screenshots needed?~
- [x] Code Reviewed
- [ ] ~Manual QA~

Release Notes:

- Clarified theme ID suffixing in extension docs

---------

Co-authored-by: Finn Evers <finn.evers@outlook.de>

Change summary

docs/src/extensions/developing-extensions.md | 2 ++
1 file changed, 2 insertions(+)

Detailed changes

docs/src/extensions/developing-extensions.md 🔗 

@@ -40,6 +40,8 @@ description = "My cool extension"
 repository = "https://github.com/your-name/my-zed-extension"
 ```
 
+> Note: If you are working on a theme extension with the intend of publishing it later, is is recommended that you suffix your theme's extension ID with `-theme`. This might otherwise be raised during the process of [releasing your extension](#publishing-your-extension).
+
 In addition to this, there are several other optional files and directories that can be used to add functionality to a Zed extension. An example directory structure of an extension that provides all capabilities is as follows:
 
 ```