Add missing `GEMINI.md` rule file for `gemini-cli` (#38885)

Junseong Park created 

This pull request adds the missing **`GEMINI.md`** file, which will
serve as the rule/configuration file for **`gemini-cli`**.

Currently, the repository includes several rule files such as
**`.clinerules`**, **`.cursorrules`**, **`.rules`**, and
**`.windsurfrules`**. Adding **`GEMINI.md`** standardizes the
configuration structure and ensures that the specific rules for the
`gemini-cli` are properly documented alongside the others.


Release Notes:

- N/A

Change summary

GEMINI.md | 1 +
1 file changed, 1 insertion(+)

Detailed changes