Reformat STYLE_GUIDE.md to wrap at 80 characters

Author: google-labs-jules[bot]

Jules.md

@@ -300,9 +300,11 @@ API documentation.
 
 ## Coding Style
 
+*   **Firebase C++ Style Guide**: For specific C++ API design and coding
+    conventions relevant to this SDK, refer to the [STYLE_GUIDE.md](STYLE_GUIDE.md).
 *   **Google C++ Style Guide**: Adhere to the
     [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html)
-    as mentioned in `CONTRIBUTING.md`.
+    as mentioned in `CONTRIBUTING.md` for general C++ style.
 *   **Formatting**: Use `python3 scripts/format_code.py -git_diff -verbose` to
     format your code before committing.