updated readme with new description

Author: tommaso-moro

README.md

@@ -595,6 +595,8 @@ export GITHUB_MCP_TOOL_ADD_ISSUE_COMMENT_DESCRIPTION="an alternative description
 
 - **list_discussions** - List discussions
   - `category`: Optional filter by discussion category ID. If provided, only discussions with this category are listed. (string, optional)
+  - `direction`: Order direction. (string, optional)
+  - `orderBy`: Order discussions by field. If provided, the 'direction' also needs to be provided. (string, optional)
   - `owner`: Repository owner (string, required)
   - `repo`: Repository name (string, required)