fix: update default base URL for subgraphs to include staging environment

Author: Le-Caignec

packages/sdk/CHANGELOG.md

@@ -6,7 +6,9 @@ All notable changes to this project will be documented in this file.
 
 ### Changed
 
-- migrated subgraphs default base URL (<https://thegraph.iex.ec>)
+- Updated the default base URL for subgraphs:
+  - Production: <https://thegraph.iex.ec>
+  - Staging: <https://thegraph-staging.iex.ec>
 
 ## [2.0.0-beta.15] (2025-04-04)