fix(docs): update version check in documentation build script to include stable versions

Author: oujago

.readthedocs.yml

@@ -17,7 +17,7 @@ build:
         echo "Building documentation for version: $CURRENT_VERSION"
 
         # Check if this is a v2 version (branch/tag starts with v2 or contains version2)
-        if [[ "$CURRENT_VERSION" == v2* ]] || [[ "$CURRENT_VERSION" == *version2* ]]; then
+        if [[ "$CURRENT_VERSION" == stable* ]] || [[ "$CURRENT_VERSION" == v2* ]] || [[ "$CURRENT_VERSION" == *version2* ]]; then
           echo "Building brainpy-version2 documentation"
           mkdir -p docs_build
           cp -r docs_version2/* docs_build/